@article{10_21136_CPM_1989_118370,
     author = {Zelinka, Bohdan},
     title = {Centers of directed cacti},
     journal = {\v{C}asopis pro p\v{e}stov\'an{\'\i} matematiky},
     pages = {225--229},
     publisher = {mathdoc},
     volume = {114},
     number = {3},
     year = {1989},
     doi = {10.21136/CPM.1989.118370},
     mrnumber = {1016631},
     zbl = {0681.05034},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/CPM.1989.118370/}
}