It is sometimes not possible to download automatically a reference; for instance, if you wish to have the reference of a book section, a legal case, an unpublished document... In this case, the reference must be entered manually.
Select "New Reference" in the menu "References", choose the right reference type (book, edited book, article, case...).
When you enter manually a reference, it is essential to follow certain rules:
Menu Edit -> Preferences -> References Types.
Click on "Modify Reference Types". Choose in the drop-down list the reference type you would like to modify, change the names of the fields, and click on OK to save.
It is also possible to create new reference types using the 3 unused reference types available.