Unranked players winning Grand Slam titles

Question

If Justine Henin can defeat Serena Williams to win the 2010 Australian Open women’s singles title, the Belgian will be just the third unranked woman to win a Grand Slam since rankings were introduced in 1975. She would follow in the footsteps of Kim Clijsters (US Open 2009) and Evonne Goolagong Cawley (Australian Open, December 1977).