@article{10_1017_S0017089500007795,
     author = {Levi, Inessa and Schein, Boris M.},
     title = {The semigroup of one-to-one transformations with finite defects},
     journal = {Glasgow mathematical journal},
     pages = {243--249},
     year = {1989},
     volume = {31},
     number = {2},
     doi = {10.1017/S0017089500007795},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500007795/}
}