BibTeX: 
@article{Relation_AlgebraAFP,
author = {Alasdair Armstrong and Simon Foster and Georg Struth and Tjark Weber},
title = {Relation Algebra},
journal = {Archive of Formal Proofs},
month = jan,
year = 2014,
note = {\url{http://isaafp.org/entries/Relation_Algebra.html},
Formal proof development},
ISSN = {2150914x},
}
