@article{MAN_1880__16_156878,
     author = {Burmester},
     title = {Ueber das bifocal - ver\"anderliche {System.} {Hierzu} 2 {Tafeln}},
     journal = {Mathematische Annalen},
     pages = {89--111},
     publisher = {mathdoc},
     volume = {16},
     year = {1880},
     zbl = {11.0615.01},
     url = {http://geodesic.mathdoc.fr/item/MAN_1880__16_156878/}
}