Editing Silicon (section)

==History==
Owing to the abundance of silicon in the [[Earth's crust]], natural silicon-based materials have been used for thousands of years. Silicon [[rock crystal]]s were familiar to various [[ancient civilizations]], such as the [[predynastic Egypt]]ians who used it for [[beads]] and small [[vases]], as well as the [[Ancient China|ancient Chinese]]. [[Glass]] containing [[silica]] was manufactured by the [[Egyptians]] since at least 1500&nbsp;BC, as well as by the ancient [[Phoenicians]]. Natural [[silicate]] compounds were also used in various types of [[Mortar (masonry)|mortar]] for construction of early human [[dwellings]].<ref name="Britannica">{{cite web |title=Silicon |url=https://www.britannica.com/science/silicon |website=[[Encyclopedia Britannica]] |access-date=22 August 2019}}</ref>

===Discovery===
[[File:Jöns Jacob Berzelius.jpg|thumb|left|upright|[[Jöns Jacob Berzelius]] discovered silicon in 1823.]]
In 1787, [[Antoine Lavoisier]] suspected that [[silica]] might be an oxide of a fundamental [[chemical element]],<ref>In his table of the elements, Lavoisier listed five "salifiable earths", ''i.e.'', ores that could be made to react with acids to produce salts (''salis'' = salt, in Latin): ''chaux'' (calcium oxide), ''magnésie'' (magnesia, magnesium oxide), ''baryte'' (barium sulfate), ''alumine'' (alumina, aluminium oxide), and ''silice'' (silica, silicon dioxide). About these "elements", Lavoisier speculates: "We are probably only acquainted as yet with a part of the metallic substances existing in nature, as all those which have a stronger affinity to oxygen than carbon possesses, are incapable, hitherto, of being reduced to a metallic state, and consequently, being only presented to our observation under the form of oxyds, are confounded with earths. It is extremely probable that barytes, which we have just now arranged with earths, is in this situation; for in many experiments it exhibits properties nearly approaching to those of metallic bodies. It is even possible that all the substances we call earths may be only metallic oxyds, irreducible by any hitherto known process." – from {{cite book|url=https://archive.org/details/elementschemist00kerrgoog/page/n217 |page= 218 |author=Lavoisier |translator= Robert Kerr |title=Elements of Chemistry|edition= 4 |location=Edinburgh, Scotland|publisher= William Creec|year= 1799}} (The original passage appears in: {{cite book|author=Lavoisier|title=Traité Élémentaire de Chimie|location=Paris|publisher= Cuchet |year=1789|volume=1|url= {{google books |plainurl=y |id=hZch3yOrayUC|page=174}} |page=174}})</ref> but the [[chemical affinity]] of silicon for oxygen is high enough that he had no means to reduce the oxide and isolate the element.{{sfn|Greenwood|Earnshaw|1997|p=328}} After an attempt to isolate silicon in 1808, [[Sir Humphry Davy]] proposed the name "silicium" for silicon, from the Latin {{Lang|la|silex}},<!-- Dictionary.com Unabridged (v 1.1) - Cite This Source si·lex –noun flint; silica. [Origin: 1585–95; < L silex, s. silic- hard stone, flint, boulder] --> ''silicis'' for flint, and adding the "-ium" ending because he believed it to be a metal.<ref>{{Cite journal|url={{google books |plainurl=y |id=Kg9GAAAAMAAJ|page=333}} |title=Electro chemical researches, on the decomposition of the earths; with observations on the metals obtained from the alkaline earths, and on the amalgam procured from ammonia |last=Davy |first=Humphry |date=1808 |publisher=W. Bowyer and J. Nichols |language=en |journal=Philosophical Transactions of the Royal Society of London |volume=98 |pages=333–370|bibcode=1808RSPT...98..333D }}. On [{{google books |plainurl=y |id=Kg9GAAAAMAAJ|page=353}} p. 353] Davy coins the name "silicium" : "Had I been so fortunate as to have obtained more certain evidences on this subject, and to have procured the metallic substances I was in search of, I should have proposed for them the names of silicium [silicon], alumium [aluminium], zirconium, and glucium [beryllium]."</ref> Most other languages use transliterated forms of Davy's name, sometimes adapted to local phonology (e.g. [[German language|German]] {{Lang|de|Silizium}}, [[Turkish language|Turkish]] ''{{Lang|tr|silisyum}}'', [[Catalan language|Catalan]] ''{{Lang|ca|silici}}'', [[Armenian language|Armenian]] {{Lang|hy|Սիլիցիում}} or ''Silitzioum''). A few others use instead a [[calque]] of the Latin root (e.g. [[Russian language|Russian]] {{Lang|ru|кремний}}, from {{Lang|ru|кремень}} "flint"; [[Greek language|Greek]] ''{{Lang|el|πυρίτιο}}'' from {{Lang|el|πυρ}} "fire"; [[Finnish language|Finnish]] {{Lang|fi|pii}} from {{Lang|fi|piikivi}} "flint", [[Czech language|Czech]] {{Lang|cs|křemík}} from {{Lang|cs|křemen}} "quartz", "flint").<ref>{{cite web |url=http://elements.vanderkrogt.net/element.php?sym=si |title=14 Silicon |publisher=Elements.vanderkrogt.net |access-date=2008-09-12}}</ref>

[[Gay-Lussac]] and [[Louis Jacques Thénard|Thénard]] are thought to have prepared impure [[amorphous silicon]] in 1811, through the heating of recently isolated [[potassium]] metal with [[silicon tetrafluoride]], but they did not purify and characterize the product, nor identify it as a new element.<ref>{{Cite book|last1=Gay-Lussac|first1=Joseph Louis|url={{google books |plainurl=y |id=ruITAAAAQAAJ|page=313}}|title=Recherches physico-chimiques, faites sur la pile: sur la préparation chimique et les propriétés du potassium et du sodium; sur la décomposition de l'acide boracique; sur les acides fluorique, muriatique et muriatique oxigéné; sur l'action chimique de la lumière; sur l'analyse végétale et animale, etc|last2=Thénard|first2=Louis Jacques baron|date=1811|publisher=Deterville|language=fr}} [{{google books |plainurl=y |id=ruITAAAAQAAJ|page=313}} pp. 313–314]; vol. 2, [{{google books |plainurl=y |id=w8YPAAAAQAAJ|page=55
}} pp. 55–65].</ref> Silicon was given its present name in 1817 by Scottish chemist [[Thomas Thomson (chemist)|Thomas Thomson]]. He retained part of Davy's name but added "-on" because he believed that silicon was a [[Nonmetal (chemistry)|nonmetal]] similar to [[boron]] and [[carbon]].<ref>{{Cite book|last1=Thomson|first1=Thomas|url=http://archive.org/details/bub_gb_zVA0AQAAMAAJ|title=A system of chemistry : in four volumes|last2=Baldwin|first2=Charles|last3=Blackwood|first3=William|last4=Baldwin|first4=Cradock|last5=Bell & Bradfute|first5=bookseller|last6=Hodges & McArthur|first6=bookseller|date=1817|publisher=London : Printed for Baldwin, Craddock, and Joy, Paternoster-Row; William Blackwood, and Bell and Bradfute, Edinburgh; and Hodges and Macarthur, Dublin|others=University of Wisconsin - Madison|page= 252}}: "The base of silica has been usually considered as a metal, and called ''silicium''. But as there is not the smallest evidence for its metallic nature, and as it bears a close resemblance to boron and carbon, it is better to class it along with these bodies, and to give it the name of ''silicon''."</ref> In 1824, [[Jöns Jacob Berzelius]] prepared amorphous silicon using approximately the same method as Gay-Lussac (reducing [[potassium fluorosilicate]] with molten potassium metal), but purifying the product to a brown powder by repeatedly washing it.<ref>See
* Berzelius announced his discovery of silicon ("silicium") in: Berzelius, J. (presented: 1823; published: 1824) [https://books.google.com/books?id=pJlPAAAAYAAJ&pg=PA46 "Undersökning af flusspatssyran och dess märkvärdigaste föreningar"] (Investigation of hydrofluoric acid and of its most noteworthy compounds), ''Kongliga Vetenskaps-Academiens Handlingar'' [Proceedings of the Royal Science Academy], '''12''' : 46–98. The isolation of silicon and its characterization are detailed in the section titled "Flussspatssyrad kisseljords sönderdelning med kalium," pp. 46–68.
* The above article was printed in German in: J.J. Berzelius (1824) [http://gallica.bnf.fr/ark:/12148/bpt6k15086x/f185.image.langEN "''II. Untersuchungen über Flussspathsäure und deren merkwürdigsten Verbindungen''"] (II. Investigations of hydrofluoric acid and its most noteworthy compounds), ''Annalen der Physik'', '''77''': 169–230. The isolation of silicon is detailed in the section titled: [http://gallica.bnf.fr/ark:/12148/bpt6k15086x/f220.image.langEN "Zersetzung der flussspaths. Kieselerde durch Kalium"] (Decomposition of silicate fluoride by potassium), pp. 204–210.
* The above article was reprinted in French in: Berzelius (1824) [{{google books |plainurl=y |id=eHmstO7CmqAC|page=337}} "Décomposition du fluate de silice par le potassium"] (Decomposition of silica fluoride by potassium), ''Annales de Chimie et de Physique'', '''27''': 337–359.
* Reprinted in English in: {{Cite journal|url={{google books |plainurl=y |id=_UwwAAAAIAAJ|page=254}}|title=On the mode of obtaining silicium, and on the characters and properties of that substance |journal=The Philosophical Magazine and Journal: Comprehending Various Branches of Science, the Liberal and Fine Arts, Agriculture, Manufactures, and Commerce|date=1825|publisher=Richard Taylor and Company|language=en|volume=65 |pages=254–267}}</ref> As a result, he is usually given credit for the element's discovery.<ref>{{cite journal |title =The discovery of the elements: XII. Other elements isolated with the aid of potassium and sodium: beryllium, boron, silicon, and aluminum|last =Weeks |first=Mary Elvira |author-link=Mary Elvira Weeks |date=1932 |journal=Journal of Chemical Education|volume=9|issue=8|pages=1386–1412 |bibcode=1932JChEd...9.1386W|doi =10.1021/ed009p1386}}</ref><ref>{{cite journal |date=2007 |journal=Russian Journal of Applied Chemistry |doi=10.1134/S1070427207120397 |title=Silicon era |last1=Voronkov |first1 =M.G. |volume=80|pages=2190–2196 |issue=12|s2cid=195240638 }}</ref> The same year, Berzelius became the first to prepare [[silicon tetrachloride]]; [[silicon tetrafluoride]] had already been prepared long before in 1771 by [[Carl Wilhelm Scheele]] by dissolving silica in [[hydrofluoric acid]].{{sfn|Greenwood|Earnshaw|1997|p=328}} In 1823 for the first time [[Jacob Berzelius]] discovered [[silicon tetrachloride]] (SiCl<sub>4</sub>).<ref name="Kipping-1937">{{Cite journal |last=Kipping |first=Frederic Stanley |date=1937-03-01 |title=The bakerian lecture organic derivatives of silicon |journal= Proceedings of the Royal Society of London, Series A |volume=159 |issue=896 |pages=139–148 |doi=10.1098/rspa.1937.0063|bibcode=1937RSPSA.159..139K |doi-access=free }}</ref> In 1846 Von Ebelman's synthesized [[tetraethyl orthosilicate]] (Si(OC<sub>2</sub>H<sub>5</sub>)<sub>4</sub>).<ref name="Muller1965">{{Cite journal |last=Muller |first=Richard |date=January 1965 |title=One hundred years of organosilicon chemistry |url=https://pubs.acs.org/doi/abs/10.1021/ed042p41 |journal=Journal of Chemical Education |language=en |volume=42 |issue=1 |pages=41 |doi=10.1021/ed042p41 |bibcode=1965JChEd..42...41M |issn=0021-9584|url-access=subscription }}</ref><ref name="Kipping-1937" />

[[File:Silicon single crystal.jpg|thumb|Single crystal of silicon grown by the [[Czochralski process]] used to make integrated circuits]]
Silicon in its more common crystalline form was not prepared until 31 years later, by [[Henri Etienne Sainte-Claire Deville|Deville]].<ref>In 1854, Deville was trying to prepare aluminium from aluminium chloride that was heavily contaminated with silicon chloride. Deville used two methods to prepare aluminium: heating aluminium chloride with sodium metal in an inert atmosphere (of hydrogen); and melting aluminium chloride with sodium chloride and then electrolyzing the mixture. In both cases, pure silicon was produced: the silicon dissolved in the molten aluminium, but crystallized upon cooling. Dissolving the crude aluminium in hydrochloric acid revealed flakes of crystallized silicon. See: Henri Sainte-Claire Deville (1854) [{{google books |plainurl=y |id=C3VFAAAAcAAJ|page=321}} "Note sur deux procédés de préparation de l'aluminium et sur une nouvelle forme du silicium"] (Note on two procedures for the preparation of aluminium and on a new form of silicon), ''Comptes rendus'', '''39''': 321–326.<br />Subsequently, Deville obtained crystalline silicon by heating the chloride or fluoride of silicon with sodium metal, isolating the amorphous silicon, then melting the amorphous form with salt and heating the mixture until most of the salt evaporated. See: {{cite journal|first=H. |last=Sainte-Claire Deville|year=1855|url={{google books |plainurl=y |id=tZhDAQAAIAAJ|page=1034}} |title=Du silicium et du titane (On silicon and titanium) |journal=Comptes rendus |volume=40|pages= 1034–1036}}</ref><ref>{{Cite web|title=Information on silicon – history, thermodynamic, chemical, physical and electronic properties|url=http://ww1.etacude.com/|access-date=2021-06-08|website=Etacude}}</ref> By [[electrolysis|electrolyzing]] a mixture of [[sodium chloride]] and [[aluminium chloride]] containing approximately 10% silicon, he was able to obtain a slightly impure [[allotrope]] of silicon in 1854.<ref>{{cite web|url=http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e01410.html |title=Silicon: History|archive-url=https://web.archive.org/web/20110727141021/http://nautilus.fis.uc.pt/st2.5/scenes-e/elem/e01410.html |archive-date=July 27, 2011|date=2011-07-27 |website=Nautilus.fis.uc.pt}}</ref> Later, more cost-effective methods have been developed to isolate several allotrope forms, the most recent being [[silicene]] in 2010.<ref name="Aufray2010">{{Cite journal |last1=Aufray |first1=B. |last2=Kara |first2=A. | last3=Vizzini |first3=S. B. |last4=Oughaddou |first4=H. |last5=LéAndri |first5=C. |last6=Ealet |first6=B. |last7=Le Lay |first7=G. |doi=10.1063/1.3419932 |title=Graphene-like silicon nanoribbons on Ag(110): A possible formation of silicene |journal=Applied Physics Letters |volume=96 |issue=18 |pages=183102 |year=2010 | bibcode=2010ApPhL..96r3102A|url=https://stars.library.ucf.edu/cgi/viewcontent.cgi?article=7963&context=facultybib2010 |url-access=subscription }}</ref><ref name="Lalmi2010">{{Cite journal |last1=Lalmi |first1=B. |last2=Oughaddou |first2=H. |last3=Enriquez |first3=H. |last4=Kara |first4=A. |last5=Vizzini |first5=S. B. |last6=Ealet |first6=B. N. |last7=Aufray |first7=B. |doi=10.1063/1.3524215 |title=Epitaxial growth of a silicene sheet |journal=Applied Physics Letters |volume=97 |issue=22 |pages=223109 |year=2010 |bibcode=2010ApPhL..97v3109L |arxiv=1204.0523|s2cid=118490651 }}</ref> Meanwhile, research on the chemistry of silicon continued; [[Friedrich Wöhler]] discovered the first volatile hydrides of silicon, synthesising [[trichlorosilane]] in 1857 and [[silane]] itself in 1858, but a detailed investigation of the [[silanes]] was only carried out in the early 20th century by [[Alfred Stock]], despite early speculation on the matter dating as far back as the beginnings of synthetic organic chemistry in the 1830s.{{sfn|Greenwood|Earnshaw|1997|p=330}}<ref>{{harvnb|Greenwood|Earnshaw|1997|pp=337–340}}</ref> Similarly, the first [[organosilicon compound]], tetraethylsilane, was synthesised by [[Charles Friedel]] and [[James Crafts]] in 1863, but detailed characterisation of organosilicon chemistry was only done in the early 20th century by [[Frederic Kipping]].{{sfn|Greenwood|Earnshaw|1997|p=328}}

Starting in the 1920s, the work of [[William Lawrence Bragg]] on [[X-ray crystallography]] elucidated the compositions of the silicates, which had previously been known from [[analytical chemistry]] but had not yet been understood, together with [[Linus Pauling]]'s development of [[crystal chemistry]] and [[Victor Goldschmidt]]'s development of [[geochemistry]]. The middle of the 20th century saw the development of the chemistry and industrial use of [[siloxane]]s and the growing use of [[silicone]] [[polymer]]s, [[elastomer]]s, and [[resin]]s. In the late 20th century, the complexity of the crystal chemistry of [[silicide]]s was mapped, along with the [[solid-state physics]] of [[Doping (semiconductor)|doped]] [[semiconductor]]s.{{sfn|Greenwood|Earnshaw|1997|p=328}}

===Silicon semiconductors===
The first [[semiconductor devices]] did not use silicon, but used [[galena]], including German [[physicist]] [[Ferdinand Braun]]'s [[crystal detector]] in 1874 and Indian physicist [[Jagadish Chandra Bose]]'s [[radio]] crystal detector in 1901.<ref name="computerhistory-timeline">{{cite web |title=Timeline |url=https://www.computerhistory.org/siliconengine/timeline/ |website=The Silicon Engine |publisher=[[Computer History Museum]] |access-date=22 August 2019}}</ref><ref name="computerhistory-1901">{{cite web |title=1901: Semiconductor Rectifiers Patented as "Cat's Whisker" Detectors |url=https://www.computerhistory.org/siliconengine/semiconductor-rectifiers-patented-as-cats-whisker-detectors/ |website=The Silicon Engine |publisher=[[Computer History Museum]] |access-date=23 August 2019}}</ref> The first silicon semiconductor device was a silicon radio crystal detector, developed by American engineer [[Greenleaf Whittier Pickard]] in 1906.<ref name="computerhistory-1901" />

In 1940, [[Russell Ohl]] discovered the [[p–n junction]] and [[photovoltaic effect]]s in silicon. In 1941, techniques for producing high-purity [[germanium]] and [[silicon crystal]]s were developed for [[radar]] [[microwave]] detector crystals during [[World War II]].<ref name="computerhistory-timeline" /> In 1947, physicist [[William Shockley]] theorized a [[Field-effect transistor|field-effect amplifier]] made from germanium and silicon, but he failed to build a working device, before eventually working with germanium instead. The first working transistor was a [[point-contact transistor]] built by [[John Bardeen]] and [[Walter Brattain]] later that year while working under Shockley.<ref>{{cite web |title=1947: Invention of the Point-Contact Transistor |url=https://www.computerhistory.org/siliconengine/invention-of-the-point-contact-transistor/ |website=The Silicon Engine |publisher=Computer History Museum |access-date=23 August 2019}}</ref> In 1954, [[physical chemist]] [[Morris Tanenbaum]] fabricated the first silicon [[junction transistor]] at [[Bell Labs]].<ref>{{cite web |title=1954: Morris Tanenbaum fabricates the first silicon transistor at Bell Labs |url=https://www.computerhistory.org/siliconengine/silicon-transistors-offer-superior-operating-characteristics/ |website=The Silicon Engine |publisher=Computer History Museum |access-date=23 August 2019}}</ref> In 1955, [[Carl Frosch]] and Lincoln Derick at Bell Labs accidentally discovered that [[silicon dioxide]] ({{chem|SiO|2}}) could be grown on silicon.<ref>{{Cite patent|number=US2802760A|title=Oxidation of semiconductive surfaces for controlled diffusion|gdate=1957-08-13|invent1=Lincoln|invent2=Frosch|inventor1-first=Derick|inventor2-first=Carl J.|url=https://patents.google.com/patent/US2802760A}}</ref><ref name="Bassett22">{{cite book |last1=Bassett |first1=Ross Knox |title=To the Digital Age: Research Labs, Start-up Companies, and the Rise of MOS Technology |date=2007 |publisher=[[Johns Hopkins University Press]] |isbn=978-0-8018-8639-3 |pages=22–23 |url=https://books.google.com/books?id=UUbB3d2UnaAC&pg=PA22}}</ref> By 1957 Frosch and Derick published their work on the first manufactured {{chem|SiO|2}} semiconductor oxide transistor: the first planar transistors, in which drain and source were adjacent at the same surface.<ref name="auto">{{Cite journal |last1=Frosch |first1=C. J. |last2=Derick |first2=L |date=1957 |title=Surface Protection and Selective Masking during Diffusion in Silicon |url=https://iopscience.iop.org/article/10.1149/1.2428650 |journal=Journal of the Electrochemical Society |language=en |volume=104 |issue=9 |pages=547 |doi=10.1149/1.2428650|url-access=subscription }}</ref> In 1959, [[Robert Noyce]] developed the first silicon-based integrated circuit at Fairchild Semiconductor, building on prior work by [[Jack Kilby]] that relied on germanium as the semiconductor. <ref>{{Cite web |last=anysilicon |date=2017-03-27 |title=The History of the Integrated Circuit |url=https://anysilicon.com/history-integrated-circuit/#:~:text=1959:%20Robert%20Noyce%20invents%20the,junction%20isolation%20at%20Sprague%20Electric. |access-date=2025-03-30 |website=AnySilicon |language=en-US}}</ref>

===Silicon Age===
[[file:MOSFET Structure.png|thumb|The [[MOSFET]], also known as the MOS transistor, is the key component of the Silicon Age. The first silicon semiconductor oxide planar transistor was made by Frosch and Derick in 1957.<ref name="auto"/>]]

The "Silicon Age" refers to the late 20th century to early 21st century.<ref name="Feldman">{{cite book |last1=Feldman |first1=Leonard C. |title=Fundamental Aspects of Silicon Oxidation |date=2001 |publisher=[[Springer Science & Business Media]] |isbn=978-3-540-41682-1 |pages=1–11 |chapter=Introduction |author1-link=Leonard Feldman |chapter-url=https://books.google.com/books?id=sV4y2-mWGNIC&pg=PA1}}</ref><ref name="Dabrowski">{{cite book |last1=Dabrowski |first1=Jarek |last2=Müssig |first2=Hans-Joachim |chapter=1.2. The Silicon Age |title=Silicon Surfaces and Formation of Interfaces: Basic Science in the Industrial World |date=2000 |publisher=[[World Scientific]] |isbn=978-981-02-3286-3 |pages=[https://archive.org/details/siliconsurfacesf0000dabr/page/3 3–13] |chapter-url=https://books.google.com/books?id=ZlefXcP3tQAC&pg=PA3 |url=https://archive.org/details/siliconsurfacesf0000dabr/page/3 }}</ref><ref name="Siffert">{{cite book |last1=Siffert |first1=Paul |last2=Krimmel |first2=Eberhard |chapter=Preface |title=Silicon: Evolution and Future of a Technology |date=2013 |publisher=[[Springer Science & Business Media]] |isbn=978-3-662-09897-4 |chapter-url=https://books.google.com/books?id=Qxj_CAAAQBAJ&pg=PR5}}</ref> This is due to silicon being the dominant material used in electronics and information technology (also known as the [[Digital Age]] or [[Information Age]]), similar to how the [[Stone Age]], [[Bronze Age]] and [[Iron Age]] were defined by the dominant materials during their respective [[Three-age system|ages of civilization]].<ref name="Feldman" />

Because silicon is an important element in high-technology semiconductor devices, many places in the world bear its name. For example, the [[Santa Clara Valley]] in California acquired the nickname [[Silicon Valley]], as the element is the base material in the [[semiconductor industry]] there. Since then, many other places have been similarly dubbed, including [[Silicon Wadi]] in Israel; [[Silicon Forest]] in Oregon; [[Silicon Hills]] in Austin, Texas; [[Silicon Slopes]] in Salt Lake City, Utah; [[Silicon Saxony]] in Germany; [[Bangalore#Economy|Silicon Valley]] in India; [[Mexicali#Silicon Border|Silicon Border]] in Mexicali, Mexico; <!-- [[Silicon Triangle]], --> [[Silicon Fen]] in Cambridge, England; [[Old Street Roundabout#Silicon Roundabout|Silicon Roundabout]] in London; [[Silicon Glen]] in Scotland; [[Silicon Gorge]] in Bristol, England; [[Silicon Alley]] in New York City; and [[Silicon Beach]] in Los Angeles.<ref>{{cite web |url=http://www.innovationjournalism.org/ij4/presentations/turouskalidavidnordfors.pdf |title=The role of journalism in creating the metaphor of Silicon Valley |last1=Uskali |first1=T. |last2=Nordfors |first2=D. |date=23 May 2007  |work=Innovation Journalism 4 Conference, Stanford University|access-date=2016-08-08 |url-status=dead |archive-url=https://web.archive.org/web/20120907002807/http://www.innovationjournalism.org/ij4/presentations/turouskalidavidnordfors.pdf |archive-date=2012-09-07 }}</ref>