@article{MOMA_1994__118_3-4_178664,
     author = {V.C. Dumir and R.J. Hans-Gills},
     title = {A {Markoff-Type} {Chain} for the {View-Obstruction} {Problem} for {Spheres} in {R4.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {205--218},
     publisher = {mathdoc},
     volume = {118},
     number = {3-4},
     year = {1994},
     zbl = {0818.52013},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1994__118_3-4_178664/}
}