How do I get my parents to quit smoking?

They’ve been smoking my whole life, and I’ve tried every way to get them to stop. My Mom is all for quitting but she can’t quit if Dad doesn’t, you know… ’cause of the temptation. Dad would just yell at me if I asked him to quit and I don’t see any way to get him to quit without him being cooperative enough to not yell at me when I ask him to. I’m concerned for my mothers health and mine also (you know, the whole secondhand smoke thing).

Thanks in advance,
Guin