@article{EUG_1991_28_a3,
     author = {Pavlos Sinopoulos},
     title = {A {New} {Generalization} of {Sine} and cosine functional equations},
     journal = {E\ensuremath{\upsilon}\ensuremath{\kappa}\ensuremath{\lambda}\ensuremath{\varepsilon}\ensuremath{\acute\iota}\ensuremath{\delta}\ensuremath{\eta}\ensuremath{\varsigma} \ensuremath{\Gamma}},
     pages = {43--49},
     year = {1991},
     volume = {28},
     language = {gr},
     url = {http://geodesic.mathdoc.fr/item/EUG_1991_28_a3/}
}