@article{MAN_1963__152_161095,
     author = {H. Wang},
     title = {Tag {Systems} and {Lag} {Systems.}},
     journal = {Mathematische Annalen},
     pages = {65--74},
     year = {1963},
     volume = {152},
     zbl = {0131.24602},
     url = {http://geodesic.mathdoc.fr/item/MAN_1963__152_161095/}
}