@article{10_4153_CJM_1971_102_8,
     author = {Karrass, A. and Solitar, D.},
     title = {The {Free} {Product} of {Two} {Groups} with a {Malnormal} {Amalgamated} {Subgroup}},
     journal = {Canadian journal of mathematics},
     pages = {933--959},
     year = {1971},
     volume = {23},
     number = {5},
     doi = {10.4153/CJM-1971-102-8},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1971-102-8/}
}