Ashbaugh, Mark S.; Chicone, Carmen C.; Cushman, Richard H. (January 1991). The Twisting Tennis Racket. Journal of Dynamics and Differential Equations. 3: 67—85. Bibcode:1991JDDE....3...67A. doi:10.1007/BF01049489.
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Ashbaugh, Mark S.; Chicone, Carmen C.; Cushman, Richard H. (January 1991). The Twisting Tennis Racket. Journal of Dynamics and Differential Equations. 3: 67—85. Bibcode:1991JDDE....3...67A. doi:10.1007/BF01049489.