REFERENCES
- Baer , R. ( 1949 ). Extension types of Abelian groups . Amer. J. Math. 71 : 461 – 490 .
- Fuchs , L. ( 1973 ). Infinite Abelian Groups . Vol. 2 . New York : Academic Press .
- Hill , P. ( 1967 ). On the classification of Abelian groups . Photocopied manuscript .
- Hill , P. , Megibben , C. ( 2003 ). Baer's extension equivalence . Illinois J. Math. 47 : 285 – 298 .
- Communicated by A. Facchini.