@article{KYB_1977_13_5_a1,
     author = {Gerhardt, Hans-Detlef},
     title = {The beginning of a mathematical simulation theory},
     journal = {Kybernetika},
     pages = {320--332},
     year = {1977},
     volume = {13},
     number = {5},
     mrnumber = {0459062},
     zbl = {0366.68074},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/KYB_1977_13_5_a1/}
}