IEEE 91/91a-1984 IEEE Standard Graphic Symbols for Logic Functions (Including and incorporating IEEE Std 91a-1991, Supplement to IEEE Standard Graphic Symbols for Logic Functions)
1991IEEE 91/91a-1991 IEEE Standard for Graphic Symbols for Logic Functions
1970IEEE 91/91a-1984 IEEE Standard Graphic Symbols for Logic Functions (Including and incorporating IEEE Std 91a-1991, Supplement to IEEE Standard Graphic Symbols for Logic Functions)