BibTeX: 
@article{ShortestPathAFP,
author = {Christine Rizkallah},
title = {An Axiomatic Characterization of the SingleSource Shortest Path Problem},
journal = {Archive of Formal Proofs},
month = may,
year = 2013,
note = {\url{http://isaafp.org/entries/ShortestPath.shtml},
Formal proof development},
ISSN = {2150914x},
}
