@article{PIM_1969_N_S_09_23_a9,
     author = {P. S. Bullen},
     title = {On {An} {Inequality} {Of} {Tchakaloff}},
     journal = {Publications de l'Institut Math\'ematique},
     pages = {69 },
     publisher = {mathdoc},
     volume = {_N_S_09},
     number = {23},
     year = {1969},
     url = {http://geodesic.mathdoc.fr/item/PIM_1969_N_S_09_23_a9/}
}