@article{GDZPPN001261193,
title = {Permutability of normal extensions of a semilattice.},
journal = {Semigroup forum},
volume = {43},
year = {1991},
pages = {151-162},
zbl = {0737.20031},
url = {http://dml.mathdoc.fr/item/GDZPPN001261193}
}
Piochi, B. Permutability of normal extensions of a semilattice.. Semigroup forum, Tome 43 (1991) pp. 151-162. http://gdmltest.u-ga.fr/item/GDZPPN001261193/