Lehmann 1995, p. 165 Lehmann, Joel (1995). "Converging Concepts of Series: Learning from History". In Swetz, Frank; Fauvel, John; Bekken, Otto; Johansson, Bengt; Katz, Victor (eds.). Learn from the Masters!(PDF). Mathematical Association of America. pp. 161–180.
Lehmann 1995, p. 176 Lehmann, Joel (1995). "Converging Concepts of Series: Learning from History". In Swetz, Frank; Fauvel, John; Bekken, Otto; Johansson, Bengt; Katz, Victor (eds.). Learn from the Masters!(PDF). Mathematical Association of America. pp. 161–180.