___

• [1] Bruce, J. W. and Giblin, P. J., Curves and singularities (2nd edition). Cambridge University Press, Cambridge, 1992.
• [2] Gomes Teixeira, F., Traité des courbes spéciales remarquables planes et gauches (reprint). Chelsea Publishing Company, New York, 1971.
• [3] Lockwood, E. H., A book of curves. Cambridge University Press, Cambridge, 1961.
• [4] Sewell, M., Parametric Envelopes. Math. Gazette 99 (2015), 226-229.