BibTeX: 
@article{Buffons_NeedleAFP,
author = {Manuel Eberl},
title = {Buffon's Needle Problem},
journal = {Archive of Formal Proofs},
month = jun,
year = 2017,
note = {\url{https://isaafp.org/entries/Buffons_Needle.html},
Formal proof development},
ISSN = {2150914x},
}
