@article{MS2_1982__50_166793,
     author = {Gustaf Gripenberg},
     title = {Volterra integral operators and logarithmic convexity.},
     journal = {Mathematica Scandinavica},
     pages = {209--220},
     publisher = {mathdoc},
     volume = {50},
     year = {1982},
     zbl = {0495.45012},
     url = {http://geodesic.mathdoc.fr/item/MS2_1982__50_166793/}
}