Watson and Crick discover chemical structure of DNA. (2013). The History Channel website. Retrieved 2:07, May 24, 2013, from http://www.history.com/this-day-in-history/watson-and-crick-discover-chemical-structure-of-dna.
Watson and Crick discover chemical structure of DNA. [Internet]. 2013. The History Channel website. Available from: http://www.history.com/this-day-in-history/watson-and-crick-discover-chemical-structure-of-dna [Accessed 24 May 2013].
“Watson and Crick discover chemical structure of DNA.” 2013. The History Channel website. May 24 2013, 2:07 http://www.history.com/this-day-in-history/watson-and-crick-discover-chemical-structure-of-dna.
“Watson and Crick discover chemical structure of DNA,” The History Channel website, 2013, http://www.history.com/this-day-in-history/watson-and-crick-discover-chemical-structure-of-dna [accessed May 24, 2013].
“Watson and Crick discover chemical structure of DNA,” The History Channel website, http://www.history.com/this-day-in-history/watson-and-crick-discover-chemical-structure-of-dna (accessed May 24, 2013).
Watson and Crick discover chemical structure of DNA [Internet]. The History Channel website; 2013 [cited 2013 May 24] Available from: http://www.history.com/this-day-in-history/watson-and-crick-discover-chemical-structure-of-dna.
Watson and Crick discover chemical structure of DNA, http://www.history.com/this-day-in-history/watson-and-crick-discover-chemical-structure-of-dna (last visited May 24, 2013).
Watson and Crick discover chemical structure of DNA. The History Channel website. 2013. Available at: http://www.history.com/this-day-in-history/watson-and-crick-discover-chemical-structure-of-dna. Accessed May 24, 2013.