REFERENCES
- Fine , B. and Rosenberger , G. 1992 . On Restricted Gromov Groups . Comm. Algebra , 20 ( 8 ) : 2171 – 2181 .
- Karrass , A. and Solitar , D. 1971 . The Free Product of Two Groups with a Malnormal Amalgamated Subgroup . Canad. J. Math. , 23 : 933 – 959 .
- Magnus , W. , Karrass , A. and Solitar , D. 1966 . “ Pure and Applied Math. ” . In Combinatorial Group Theory Vol. XIII , New York-London-Sydney : Wiley-Interscience .
- Serre , J.P. 1980 . New York , , Berlin-Heidelberg : Trees Springer-Verlag .