1. C. Chicone andN. J. Kalton, Flat Embeddings of the Möbius Strip in ?3. Preprint, Department of Mathematics, University of Missouri, Columbia, 1984.
2. H.Flanders, Differential Forms. Mathematics in Science and Engineering, New York 1963.
3. W. C.Graustein, Differential Geometry. New York 1966.
4. T.Randrup and P.RØgen, How to Twist a Knot. Master of Science Thesis, Mathematical Institute, Technical University of Denmark, January 1995.
5. G. Schwarz, The Dark Side of the Moebius Strip. Amer. Math. Monthly97, 890?897 (1990).