When writing, it is important to recognize the support from the documentary sources you used. Otherwise, you commit plagiarism by passing off the work or thoughts of another as your own. It is also essential that readers be able to find and consult these sources and use them in their own work.
For example, if a technical report or maintenance procedure simply states that "we used a Canadian vibration standard", how the engineer is supposed to find the appropriate standard without its number or publication year?
When it comes to citing maps and geospatial data, we recommend you to check the following resources:
Guide made by the University of Texas at Arlington : APA and MLA styles