@article{IIGUM_2020_32_a4,
     author = {A. V. Litavrin},
     title = {Endomorphisms of some groupoids of order $k+k^2$},
     journal = {The Bulletin of Irkutsk State University. Series Mathematics},
     pages = {64--78},
     publisher = {mathdoc},
     volume = {32},
     year = {2020},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IIGUM_2020_32_a4/}
}