The works of L. Euler, volume 3
E156 is one of an unusual group of Eneström numbers. It refers to a collection of articles which were published together (in this case E109, E173, and E174), but were written on different topics. Sometimes referred to as Opuscula Varii Argumenti, Volume 3, this work is part of a three-volume series, the other two parts being E80 (Volume 1) and E121 (Volume 2).
Original Source Citation
Nova acta eruditorum, Volume 1755, pp. 500-516.