Hello, I started a project from an imported SDK example with MCUXpresso V10.3. It was been built successfully before I added exist source files. After adding some exist source files in to the project by Import-->Files System, I meet the problem "undefined reference to xxx". I have added referred directory in "Include paths". I checked "sources.mk", in the SUBDIRS section, the referred directory named "CANopen" isn't included. How can I manage this?