\bibitem{Saam00}        B.T.~Saam, D.A.~Yablonskiy, V.D.~Kodibagkar, J.C.~Leawoods, D.S.~Gierada, J.D.~Cooper, S.S.~Lefrak, M.S.~Conradi,
                        {\it MR Imaging of Diffusion of He-3 Gas in Healthy and Diseased Lungs},
                        Magn.~Res.~Med. {\bf 44}, 174, 2000.