BibTeX: 
@article{Bertrands_PostulateAFP,
author = {Julian Biendarra and Manuel Eberl},
title = {Bertrand's postulate},
journal = {Archive of Formal Proofs},
month = jan,
year = 2017,
note = {\url{http://isaafp.org/entries/Bertrands_Postulate.html},
Formal proof development},
ISSN = {2150914x},
}
