@article{ZR_1977_2_10_a10,
     author = {B. S. Ste\v{c}kin},
     title = {Several {Combinators} {Problems}},
     journal = {Zbornik radova},
     pages = {129 },
     year = {1977},
     volume = {2},
     number = {10},
     url = {http://geodesic.mathdoc.fr/item/ZR_1977_2_10_a10/}
}