How to compare model fits

What is a good way to compare nested models? For example, I have some proc mixed models like this, which are the same except for the fixed effects. :

PROC MIXED DATA=All;
CLASS Subject;
MODEL A =B C;
RANDOM intercept /subject=Subject;
Run;

PROC MIXED DATA=All;
CLASS Subject;
MODEL A =B C D;
RANDOM intercept /subject=Subject;
Run;

I know I can compare the AICs and BICs - but I'm not sure how SAS can do a likelihood ratio test. Any suggestions would be appreciated.