references not being cited!

Question

I do not know why those two references can not get cited. I only get a question mark instead of the reference number. I copy the name of the reference and I still have the error!. Here is what I write: \cite{Agembeddedinsi} and it does not work!!!

@article{Agembeddedinsi,
   author = "Trolle, Mads L. and Pedersen, Thomas G.",
   title = "Indirect optical absorption in silicon via thin-film surface plasmon",
   journal = "Journal of Applied Physics",
   year = "2012",
   volume = "112",
   number = "4", 
   eid = 043103,
   pages = "-",
   url = "http://scitation.aip.org/content/aip/journal/jap/112/4/10.1063/1.4746699",
   doi = "http://dx.doi.org/10.1063/1.4746699" 
}

@article{organicdiodes,
   author = "Ditlbacher, H. and Aussenegg, F. R. and Krenn, J. R. and Lamprecht, B. and Jakopic, G. and Leising, G.",
   title = "Organic diodes as monolithically integrated surface plasmon polariton detectors",
   journal = "Applied Physics Letters",
   year = "2006",
   volume = "89",
   number = "16", 
   eid = 161101,
   pages = "-",
   url = "http://scitation.aip.org/content/aip/journal/apl/89/16/10.1063/1.2362975",
   doi = "http://dx.doi.org/10.1063/1.2362975" 
}