@article{MV_1976_28_2_a12,
     author = {A. Torga\v{s}ev},
     title = {Roots of positive and negative operators on {Wachs} spaces},
     journal = {Matemati\v{c}ki vesnik},
     pages = {227 },
     year = {1976},
     volume = {28},
     number = {2},
     url = {http://geodesic.mathdoc.fr/item/MV_1976_28_2_a12/}
}