You have been given the information. Check out Wikipedia: http://en.wikipedia.org/wiki/John_A._Lejeune
or hear Laura Lejeune discuss the pronunciation of her name in an interview with Charles Gaddy here: http://www.youtube.com/watch?v=WAoDaeszggI&feature=related
Just say it properly and you will know that you are doing the right thing and those who continue to say "lejoon" just simply don't know any better. It is a matter of respect and bottom line-everyone deserves to have their name pronounced correctly!
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