[xwiki-users] Fetch application fields from other applications

Hi, I have created two applications, let's say one for managing clients and one for managing projects. How can I fetch the clients name and use it in my list of projects? To speak in database terms I want my project's table to have a foreign key which refers to the client primary key so that I can access all client's attributes. Would be thankful for inspiration or helpful links to existing(?) tutorials. Thanks and bests, Moritz