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@article{CM_1951__9__130_0, author = {Loonstra, F.}, title = {The classes of partially ordered groups}, journal = {Compositio Mathematica}, pages = {130--140}, publisher = {Kraus Reprint}, volume = {9}, year = {1951}, mrnumber = {45740}, zbl = {0043.25602}, language = {en}, url = {http://geodesic.mathdoc.fr/item/CM_1951__9__130_0/} }
Loonstra, F. The classes of partially ordered groups. Compositio Mathematica, Tome 9 (1951), pp. 130-140. http://geodesic.mathdoc.fr/item/CM_1951__9__130_0/