1. W. Siegel, Covariant approach to superstrings, in Symposium on anomalies, geometry, topology, Chicago U.S.A. (1985), W.A. Bardeen and A.R. White eds., World Scientific, Singapore (1985), pg. 348.
2. W. Siegel, Covariant superstrings, in Unified string theories, Santa Barbara U.S.A. (1985), M. Green and D. Gross eds., World Scientific, Singapore (1985), pg. 559.
3. W. Siegel, Classical Superstring Mechanics, Nucl. Phys. B 263 (1986) 93 [
INSPIRE
].
4. W. Siegel, Randomizing the superstring, Phys. Rev. D 50 (1994) 2799 [
hep-th/9403144
] [
INSPIRE
].
5. M.J. Duff, Duality Rotations in String Theory, Nucl. Phys. B 335 (1990) 610 [
INSPIRE
].