1. Feldman, E.A.: Immersions with nowhere vanishing mean curvature vector. Top12, 201–227 (1973)
2. Gromov, M.: Stable mappings of foliations into manifolds. Izv. Akad. Nauk. S.S.S.R. Ser. Mat.33, 707–734 (1969); Math U.S.S.R. Izv.3, 671–694 (1969)
3. Lawson, H.B., Jr., Michelsohn, M.-L.: Embedding and surrounding with positive mean curvature. Invent. Math.77, 399–419 (1984)
4. Phillips, A.: Submersion of open manifolds. Top6, 171–206 (1967)
5. Steenrod, N.: The topology of Fibre Bundles. Princeton N. J.: Princeton Univ. Press, 1951