Eclipse中Maven [Compile Error]中的多个额外源目录

i'm working on a "complex"/"well-structured" Maven Project, and in particular i'm working on a single internal Module of the project. I'm against a COMPILE ERROR because it seems that it doesn't find the Java Classes from an external source already linked from the Menu (right-clicking on the project) ->Build Path->Link Source. This is a bunch of essential errors taken from the Console when i Run-> mvn : compilei'm working on a "complex"/"well-structured" Ma