@article{oai:niigata-u.repo.nii.ac.jp:00002096, author = {Innami, Nobuhiro}, issue = {2}, journal = {Journal of the Mathematical Society of Japan, Journal of the Mathematical Society of Japan}, month = {}, pages = {251--261}, title = {Manifolds without conjugate points and with integral curvature zero}, volume = {41}, year = {1989} }