@article{GDZPPN00125166X,
title = {Semilattices of width 2.},
journal = {Semigroup forum},
volume = {12},
year = {1976},
pages = {149-177},
zbl = {0354.06001},
url = {http://dml.mathdoc.fr/item/GDZPPN00125166X}
}
Sirjaev, V.M. Semilattices of width 2.. Semigroup forum, Tome 12 (1976) pp. 149-177. http://gdmltest.u-ga.fr/item/GDZPPN00125166X/