@article{ITA_2009__43_2_209_0,
     author = {Halava, Vesa and Harju, Tero and K\"arki, Tomi},
     title = {The theorem of {Fine} and {Wilf} for relational periods},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {209--220},
     publisher = {EDP-Sciences},
     volume = {43},
     number = {2},
     year = {2009},
     doi = {10.1051/ita:2008025},
     mrnumber = {2512255},
     zbl = {1166.68035},
     language = {en},
     url = {http://www.numdam.org/articles/10.1051/ita:2008025/}
}