sports card price guide

I need help finding a reliable price of sports cards is updated.?
I have many old maps as a map of Donovan McNabb, Rookie of the world in 1999, Dan Marino 1986 World Map. I try to get an account at the price because I want to sell and personally, I do not charge. Any help finding priced reputable online guide would be helpful.
www.beckett.com Beckett is the industry leader in the sports cards.
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