This is a targetted offer, so unfortunately you’re out of luck if you didn’t receive the e-mail. According to this thread at FW, you might be solicited for this offer if you already have a Citi Student card. Basically, for each person you refer that applies and is approved for a Citi Card for College Students through the link provided in the e-mail, you’ll receive a $100 statement credit, up to a maximum of 5 approved accounts.

Your referrals must apply by October 31, 2006 to qualify.