I have a table called citizens with a primary key called cpr. 
I have another table called care. In this table, I have also created a column with the name cpr. When I go into the Foreign Keys tab, I enter fk_citizen_cpr as the foreign key name, and reference the citizens table. Then I see checkboxes for the columns in the citizens table, but I can't check cpr or any of them for that matter.  
What am I doing wrong? Thanks.
