@article{NSJOM_1991_21_1a_8,
     author = {Popa Valeriu},
     title = {Fixed points on two 

 complete metric spaces},
     journal = {Novi Sad Journal of Mathematics},
     pages = {83-93},
     publisher = {mathdoc},
     volume = {21},
     number = {1},
     year = {1991},
     url = {http://geodesic.mathdoc.fr/item/NSJOM_1991_21_1a_8/}
}