@article{SF_1977__14_186363,
     author = {E. V. Sukhanov},
     title = {The groupoid of varieties of idempotent semigroups.},
     journal = {Semigroup forum},
     pages = {143--160},
     publisher = {mathdoc},
     volume = {14},
     year = {1977},
     zbl = {0366.20043},
     url = {http://geodesic.mathdoc.fr/item/SF_1977__14_186363/}
}