@article{AM2_1983__26_136988,
     author = {Abraham Ungar},
     title = {Addition theorems for solutions to linear homogeneous constant coefficient ordinary differential equations.},
     journal = {Aequationes mathematicae},
     pages = {104--112},
     publisher = {mathdoc},
     volume = {26},
     year = {1983},
     zbl = {0546.34006},
     url = {http://geodesic.mathdoc.fr/item/AM2_1983__26_136988/}
}