@article{SF_1989__39_2_134983,
     author = {L.M. Martynov},
     title = {On spectra of solvability and attainability for varieties of semigroups.},
     journal = {Semigroup forum},
     pages = {129--156},
     publisher = {mathdoc},
     volume = {39},
     number = {2},
     year = {1989},
     zbl = {0679.20053},
     url = {http://geodesic.mathdoc.fr/item/SF_1989__39_2_134983/}
}