en Rees, E. L. (). „Graphical Discussion of the Roots of a Quartic Equation”. The American Mathematical Monthly. 29 (2): 51–55. doi:10.2307/2972804. JSTOR2972804.
en Lazard, D. (). „Quantifier elimination: Optimal solution for two classical examples”. Journal of Symbolic Computation. 5 (1–2): 261–266. doi:10.1016/S0747-7171(88)80015-4.
jstor.org
en Rees, E. L. (). „Graphical Discussion of the Roots of a Quartic Equation”. The American Mathematical Monthly. 29 (2): 51–55. doi:10.2307/2972804. JSTOR2972804.