Which website(s) are considered the "official source" (if there is such a thing) in giving value for individual Pokemon cards? Including Japanese ones.

I have a shit ton of old holo cards in a book I dug up from years ago and want to sell them. So far I've done fine getting values from 4 or 5 different sites, but before I get too far into it I want to make sure people won't bitch that I didn't use the "right site" for prices.... I plan on selling them all together as one book.

So far I've been using http://pokemonprices.com/ because it can gather the average price from a bunch of different listings around the web, which I've been using for the most part.