@article{oai:tsukuba.repo.nii.ac.jp:00039408, author = {DRAGOMIR, Sorin and DUGGAL, Krishan L.}, issue = {2}, journal = {Tsukuba Journal of Mathematics}, month = {Oct}, pages = {335--348}, title = {Indefinite Extrinsic Spheres}, volume = {32}, year = {2008} }