@article{KYB_1988__24_1_a7,
     author = {Bebj\'ak, Andrej and \v{S}tef\'anekov\'a, Ivana},
     title = {Nondeterminism is essential for reversal-bounded two-way multihead finite automata},
     journal = {Kybernetika},
     pages = {65--71},
     publisher = {mathdoc},
     volume = {24},
     number = {1},
     year = {1988},
     mrnumber = {936556},
     zbl = {0648.68063},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/KYB_1988__24_1_a7/}
}