Churchill, Robert Paul (1990). Logic: An Introduction (2nd edición). New York: St. Martin's Press. p. 418. ISBN0-312-02353-7. OCLC21216829. «In his book A System of Logic (1843), Mill proposed four methods for testing causal hypotheses: the method of agreement, the method of difference, the joint method of agreement and difference, and the method of concomitant variation.7 (footnote 7: Mill also proposed a fifth method, which he called the method of residues.)».
Churchill, Robert Paul (1990). Logic: An Introduction (2nd edición). New York: St. Martin's Press. p. 418. ISBN0-312-02353-7. OCLC21216829. «In his book A System of Logic (1843), Mill proposed four methods for testing causal hypotheses: the method of agreement, the method of difference, the joint method of agreement and difference, and the method of concomitant variation.7 (footnote 7: Mill also proposed a fifth method, which he called the method of residues.)».
