@article{ITA_2001__35_1_61_0,
     author = {Poll, Erik},
     title = {A coalgebraic semantics of subtyping},
     journal = {RAIRO - Theoretical Informatics and Applications - Informatique Th\'eorique et Applications},
     pages = {61--81},
     publisher = {EDP-Sciences},
     volume = {35},
     number = {1},
     year = {2001},
     mrnumber = {1845875},
     zbl = {0990.18004},
     language = {en},
     url = {http://archive.numdam.org/item/ITA_2001__35_1_61_0/}
}