1. Abel,N. H., Sur les fonctions génératrices et leurs déterminantes. InOeuvres Complètes de N. H. Abel (Ed.B. Holmboe)Tome Second (Christiania: Grøndahl, 1839), 77?88. Also inOeuvres Complètes de Niels Henrik Abel (Ed.L. Sylow &S. Lie)Tome Second (Christiania: Grøndahl, 1881), 67?81.
2. Bessel,F. W., Über die Theorie der Zahlenfacultäten.Königsber. Archiv. f. Naturwiss. Math. 1 (1812), 241?270, 463. Also inAbhandlungen von Friedrich Wilhelm Bessel (Ed.R. Engelmann) (Leipzig: Engelmann, 1876)2, V, 342?352.
3. Boole,G., On a general method in analysis.Phil. Trans. 136 (1844), 225?282.
4. [G. Boole], On the integration of linear differential equations with constant coefficients.Cambridge Math. J. 1. Ser 2 (1840, 841), 114?119.
5. Boole,G.,A Treatise on Differential Equations (Cambridge: Macmillan, 1859; 2nd Edn.ibid. 1865; 2nd Edn. reprinted as 5th Edn. New York: Chelsea, n.d. [1959?]).