@article{DCG_1994__11_3_131302,
     author = {J.H. Reif and J.D. Tygar and A. Yoshida},
     title = {Computability and {Complexity} of {Ray} {Tracing.}},
     journal = {Discrete & computational geometry},
     pages = {265--288},
     publisher = {mathdoc},
     volume = {11},
     number = {3},
     year = {1994},
     zbl = {0807.68096},
     url = {http://geodesic.mathdoc.fr/item/DCG_1994__11_3_131302/}
}