Alter Table problems

I am attempting to add a few attributes to an existing table that already
contains data. The problem that I am having is that the new attributes
that I want to add need to be forgein key references to other tables. I
can't figure out how to create the attribute with a reference to another
table. I tried the following, but all it did was create the
attribute... no forgein key:

ALTER TABLE student ADD COLUMN major REFERENCES degree_major;

I was also wondering how I would DELETE an attribute from an existing
table... i.e. ALTER TABLE student DELETE COLUMN major;

Any help would be much appreciated. Thanks.

-Scott