@article{SF_1980__20_134400,
     author = {M.B. Szendrei},
     title = {On a pull-back diagram for orthodox semigroups.},
     journal = {Semigroup forum},
     pages = {1--10},
     publisher = {mathdoc},
     volume = {20},
     year = {1980},
     zbl = {0438.20046},
     url = {http://geodesic.mathdoc.fr/item/SF_1980__20_134400/}
}