\bibitem{Saam99}        B.T.~Saam, D.A.~Yablonskiy, D.S.~Gierada, M.S.~Conradi,
                        {\it Rapid Imaging of Hyperpolarized Gas Using EPI},
                        Magn.~Res.~Med. {\bf 42}, 507, 1999.