Bez, Helmut The invariant functions and invariant-image conditions of the rational Bézier triangles The invariant functions and invariant-image conditions of the rational Bézier triangles Rational parametrisation;Geometric modeling;Transformation groups;Invariant functions;Information and Computing Sciences not elsewhere classified 2014-05-27
    https://repository.lboro.ac.uk/articles/journal_contribution/The_invariant_functions_and_invariant-image_conditions_of_the_rational_B_zier_triangles/9402521