Six independent papers reporting epitaxial formation of silicene in 2012 According to a Nature news article cited below (info-box "The rise of silicone"), six independent papers were published reporting successful epitaxial formation of silicene.
Does anyone know which those were? I am just able to find the following two papers:


Fleurence, A., R. Friedlein, T. Ozaki, H. Kawai, Y. Wang, Y.
Yamada-Takamura (2012). "Experimental evidence for epitaxial silicene
on diboride thin films". Physical Review Letters 108(24)
Vogt, P., P. De Padova, C. Quaresima, J. Avila, E. Frantzeskakis, M.C. Asensio, A. Resta, B. Ealet, G. Le Lay (2012). "Silicene: compelling experimental evidence for graphenelike two-dimensional silicon". Physical Review Letters 108(15)
Nature (2015). "Graphene’s cousin silicene makes transistor debut". Nature news article. URL: http://www.nature.com/news/graphene-s-cousin-silicene-makes-transistor-debut-1.16839


Does anyone know where to find the other four?
Since this is a Nature News article, usually it is a way of promoting a scientific article in one of the current Nature publications - that's why it can get away with stating "Six independent reports" without six citations attached.  In this case, it is citing this 2015 article: 


  Tao, L. et al. Nature Nanotechnol.
  http://dx.doi.org/10.1038/NNANO.2014.325 (2015)


There are many citations in that article from the 2010-2013 time period reporting silicene sheets and nanoribbons.  Keep in mind, the Fleurence et al. paper you mentioned might not be one of the six mentioned, because it uses a diboride substrate instead of silver.