@article{AL_1984_23_6_a6,
     author = {L. A. Shemetkov},
     title = {The product of formations of algebraic systems},
     journal = {Algebra i logika},
     pages = {721--729},
     year = {1984},
     volume = {23},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/AL_1984_23_6_a6/}
}