Gassian is a general purpose computational chemistry software released by Gassian Inc.
Gaussian 16W (Windows)
Gaussian 16 Utilities (Windows)
The citation should include:
a. the name of the product: Gaussian 16
b. the source: Gaussian, Inc.m 340 Quinnipiac Street, Building 40, Wallingford, CT 06492
c. the authorship as designated by GAUSSIAN