@article{SF_1972__5_133923,
     author = {E.Ja. Gabovic and G.J. Rubanovic},
     title = {The lattice of convex subgroupoids of an ordered groupoid.},
     journal = {Semigroup forum},
     pages = {54--64},
     publisher = {mathdoc},
     volume = {5},
     year = {1972},
     zbl = {0264.06012},
     url = {http://geodesic.mathdoc.fr/item/SF_1972__5_133923/}
}