The University of Waterloo's Geospatial Centre has a list of the best practices regarding citations for cartographic materials.
There are several ways to cite geospatial resources. Each of these citations are made using the Chicago Manual of Style 17th Edition, chapters 14.257,
The importance of citations is to ensure that the reader is able to find the exact resource that you used, keep this in mind when creating citations.
Author. Title. File Format. Last modified date [if available;if not, include date of access]. URL.
Author. Software name (version information). Format. City: Publisher, Year Published. URL [If available]