@article{GDZPPN00126379X,
title = {A concept of variety for regular biordered sets.},
journal = {Semigroup forum},
volume = {48},
year = {1994},
pages = {335-348},
zbl = {0814.20041},
url = {http://dml.mathdoc.fr/item/GDZPPN00126379X}
}
Broeksteeg, R. A concept of variety for regular biordered sets.. Semigroup forum, Tome 48 (1994) pp. 335-348. http://gdmltest.u-ga.fr/item/GDZPPN00126379X/