@article{PM_1992_1992_1_a19,
     author = {Demetropoulou Psomopoulou, Demetra},
     title = {Estructuras-G1 de segundo orden.},
     journal = {Publicacions matem\`atiques},
     pages = {51-64},
     year = {1992},
     volume = {36},
     number = {1},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PM_1992_1992_1_a19/}
}