@article{03996183, title = {Functional differential equations - a reciprocity principle.}, journal = {International Journal of Mathematics and Mathematical Sciences}, volume = {9}, year = {1986}, pages = {807-810}, doi = {10.1155/S0161171286000996}, zbl = {0615.34063}, language = {en}, url = {http://dml.mathdoc.fr/item/03996183} }
Williams, Lloyd K. Functional differential equations - a reciprocity principle.. International Journal of Mathematics and Mathematical Sciences, Tome 9 (1986) pp. 807-810. doi : 10.1155/S0161171286000996. http://gdmltest.u-ga.fr/item/03996183/