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2. Basic Ideas and Concepts of Differential Geometry;Alekseevskij,1991
3. Eine Invariantentheorie der 3-Gewebe aus r-dimensionalen Mannigfaltigkeiten in R 2r Abh;Chern;Math. Sem. Univ. Hamburg,1936
4. Characteristic Classes;John,1974
5. Geometry of Jet Spaces and Nonlinear Differential Equations;Krasilshchik,1986