BibTeX: 
@article{FreeBooleanAlgebraAFP,
author = {Brian Huffman},
title = {Free Boolean Algebra},
journal = {Archive of Formal Proofs},
month = mar,
year = 2010,
note = {\url{http://isaafp.org/entries/FreeBooleanAlgebra.html},
Formal proof development},
ISSN = {2150914x},
}
