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[166] Lombardo Rend. März 1871.
[167] Grunerts Arch. 56.
[168] Math. Ann. 23.
[169] Lombardo Rend. 1884; Annali di Matem. II, 12.
[170] Math. Ann. 13; Lincei Mem. 1876-1877.
[171] Napoli Rend. 1881.
[172] Journ. für Math. 78.
[173] Lombardo Rend. 1879.
[174] Acta math. 5.