@article{10_4153_CJM_1973_117_7,
     author = {Burns, R. G.},
     title = {Finitely {Generated} {Subgroups} of {HNN} {Groups}},
     journal = {Canadian journal of mathematics},
     pages = {1103--1112},
     year = {1973},
     volume = {25},
     number = {5},
     doi = {10.4153/CJM-1973-117-7},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1973-117-7/}
}