@article{SF_1983__26_134609,
     author = {D. Schweigert},
     title = {On varieties of clones.},
     journal = {Semigroup forum},
     pages = {275--286},
     year = {1983},
     volume = {26},
     zbl = {0518.08004},
     url = {http://geodesic.mathdoc.fr/item/SF_1983__26_134609/}
}