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