@article{KYB_1990_26_3_a6,
     author = {Zima, V\'aclav and Schwelb, Otto},
     title = {Semireciprocal wave propagation},
     journal = {Kybernetika},
     pages = {248--268},
     year = {1990},
     volume = {26},
     number = {3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/KYB_1990_26_3_a6/}
}