@article{1077470392,
author = {Barrett, John H.},
title = {Two-point boundary problems for linear self-adjoint
differential equations of the fourth order with middle term},
journal = {Duke Math. J.},
volume = {29},
number = {1},
year = {1962},
pages = { 543-554},
language = {en},
url = {http://dml.mathdoc.fr/item/1077470392}
}
Barrett, John H. Two-point boundary problems for linear self-adjoint
differential equations of the fourth order with middle term. Duke Math. J., Tome 29 (1962) no. 1, pp. 543-554. http://gdmltest.u-ga.fr/item/1077470392/