@article{10_1017_S0017089506003223,
     author = {STOTHERS, W. W.},
     title = {CONGRUENCE {AND} {NON-CONGRUENCE} {SUBGROUPS} {OF} {THE} {(2,3,7)-GROUP}},
     journal = {Glasgow mathematical journal},
     pages = {351--363},
     year = {2006},
     volume = {48},
     number = {3},
     doi = {10.1017/S0017089506003223},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089506003223/}
}