The American Copy Editors Society Twitter chat on Feb. 17 was about building your reference library.

Reading the Storify of the chat can give you some good ideas about things that ought to be in your resource stack.

Of course, one question is whether that library really needs shelves. I like to keep my paper copy of the AP Stylebook because sometimes it’s easier to look up what you don’t know by browsing. Online you have to have something to put in the search. (I feel even more that way about keeping a bound dictionary.)

But I admit that I do 90 percent of my lookups for grammar, style, spelling and fact checks online these days.

The key is to find trusted sources. I’m a big believer in finding the “about” page of every website I use as a resource. It will help you determine legitimacy.

I also have a rule of thumb — find the answer in more than one place, and make sure they match.

OK, so maybe I don’t do that with the regular dictionary. I trust Merriam-Webster, although I use other online dictionaries as well — I love Wordnik.com — because they offer different synonyms and examples. But when I’m fact checking, I don’t usually trust one source.

Many people will go to Wikipedia, which pops up first, but it can be an iffy source. However, it also can be a good jumping off point.

I recently checked a poll that used Census Bureau data, then I checked the Census Bureau website. The two didn’t agree. So who do you believe?  Sometimes you have to make judgments (I took the Census Bureau numbers, which were up to date). But finding the numbers in a third source helped.

It’s like adding a long column of numbers. I always do it twice. If the sums don’t agree, I’ll add them up at least two more times. Better safe than sorry.