Rules for Drawing Style 1 Symbols: PNINIP device (Example of a complex device with multiple emitters and bases).
(in English) (1993)  315-1975 - IEEE Standard American National Standard Canadian Standard Graphic Symbols for Electrical and Electronics Diagrams (Including Reference Designation Letters), IEEE, p. 118  DOI:  10.1109/IEEESTD.1993.93397. ISBN:  0738109479.
Michel Bakni