@article{NSJOM_1992_22_1a_13,
     author = {Konopka 

 Czes{\l}aw,},
     title = {On extrinsic spheres in 

 a locally product riemannian manifold},
     journal = {Novi Sad Journal of Mathematics},
     pages = {141-148},
     publisher = {mathdoc},
     volume = {22},
     number = {1},
     year = {1992},
     url = {http://geodesic.mathdoc.fr/item/NSJOM_1992_22_1a_13/}
}