@article{BAG_1990__30_138467,
     author = {H. Martini},
     title = {A contribution to the light field theory},
     journal = {Beitr\"age zur Algebra und Geometrie},
     pages = {193--202},
     year = {1990},
     volume = {30},
     url = {http://geodesic.mathdoc.fr/item/BAG_1990__30_138467/}
}