@article{MZ_1973__132_171919,
     author = {Martin Tretkoff},
     title = {The {Residual} {Finiteness} of {Certain} {Amalgameted} {Free} {Products.}},
     journal = {Mathematische Zeitschrift},
     pages = {179--182},
     publisher = {mathdoc},
     volume = {132},
     year = {1973},
     zbl = {0251.20034},
     url = {http://geodesic.mathdoc.fr/item/MZ_1973__132_171919/}
}