@article{10_1017_S0017089518000277,
     author = {TERAMOTO, KEISUKE},
     title = {FOCAL {SURFACES} {OF} {WAVE} {FRONTS} {IN} {THE} {EUCLIDEAN} {3-SPACE}},
     journal = {Glasgow mathematical journal},
     pages = {425--440},
     year = {2019},
     volume = {61},
     number = {2},
     doi = {10.1017/S0017089518000277},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089518000277/}
}