@article{AM2_1981__23_136908,
     author = {C.S. Hartzman and D.R. Naugler},
     title = {Separatrix conditions yielding either periodic orbits or unusual behavior for flows on {M3.}},
     journal = {Aequationes mathematicae},
     pages = {175--187},
     publisher = {mathdoc},
     volume = {23},
     year = {1981},
     zbl = {0539.58029},
     url = {http://geodesic.mathdoc.fr/item/AM2_1981__23_136908/}
}