@article{AM2_1969__2_182320,
     author = {E. LUK\'ACS},
     title = {Non-Negative {Definite} {Solutions} of {Certain} {Differential} and {Functional} {Equations} {Reports} of {Meetings}},
     journal = {Aequationes mathematicae},
     pages = {137--143},
     publisher = {mathdoc},
     volume = {2},
     year = {1969},
     zbl = {0174.20203},
     url = {http://geodesic.mathdoc.fr/item/AM2_1969__2_182320/}
}