Hi! I'm working on a db but i'm kinda new to this so i've bumped into a problem today. I've got some tables: OFFICE, ROOM, EMPLOYEE and DOCUMENT. Document must specify the sender, which can be a single employee, an entire room or an entire office so it must have a reference to the primary keys of those tables. Should I do a "parallel" table for handle it (for example i've done one for handle the multiple recipients documents) or there is another way? Thank you