@article{NSJOM_1999_29_3a_36,
     author = {Lj. S. 

 Velimirovi\'c},
     title = {On 

 variation of the volume under infinitesimal bending of a closed rotational 

 surface},
     journal = {Novi Sad Journal of Mathematics},
     pages = {377-386},
     year = {1999},
     volume = {29},
     number = {3},
     url = {http://geodesic.mathdoc.fr/item/NSJOM_1999_29_3a_36/}
}