@article{JGG_2021_25_1_JGG_2021_25_1_a0,
     author = {B. Odehnal},
     title = {Isoptic {Ruled} {Surfaces} of {Developable} {Surfaces}},
     journal = {Journal for geometry and graphics},
     pages = {1--17},
     year = {2021},
     volume = {25},
     number = {1},
     url = {http://geodesic.mathdoc.fr/item/JGG_2021_25_1_JGG_2021_25_1_a0/}
}