@article{JGG_2008_12_2_JGG_2008_12_2_a0,
     author = {P. Koltsaki and D. Papadopoulou },
     title = {Orthogonal {Line} {Congruences} with {Common} {Middle} {Surface}},
     journal = {Journal for geometry and graphics},
     pages = {123--132},
     publisher = {mathdoc},
     volume = {12},
     number = {2},
     year = {2008},
     url = {http://geodesic.mathdoc.fr/item/JGG_2008_12_2_JGG_2008_12_2_a0/}
}