References and Namespaces

Hi,

My question is a little bit frustrating for me. Currently on my project there are two different Assembly definitions and 2 different namespaces. And my A.cs script is on my X namespace and Assembly-Csharp definition. And my B.cs script is on my Project namespace and Project-Assembly definition. What I am trying to do is, inside B script, I want to create a variable which is A.cs type but initially I can't. I tried to double click on my project assembly and i added Assembly-Csharp as a reference. I am able to Create a A type under my B until i save. Eventually it discards the reference adding after saving. Are there any options for this ? Thank you.

Best regards.