If you no index a page, link juice will flow to that page still. if you no follow it, it will still flow but will not flow out of it again.
you should always add noindex,follow if you want the link juice to return to your index pages. Even then some link juice will be lost that stays on that noindex page
I tried also could not find it. but here is a quote from Matt Cutts "Eric Enge: Can a NoIndex page accumulate PageRank?
Matt Cutts: A NoIndex page can accumulate PageRank, because the links are still followed outwards from a NoIndex page.
Eric Enge: So, it can accumulate and pass PageRank.
Matt Cutts: Right, and it will still accumulate PageRank, but it won't be showing in our Index. So, I wouldn't make a NoIndex page that itself is a dead end. You can make a NoIndex page that has links to lots of other pages.
For example you might want to have a master Sitemap page and for whatever reason NoIndex that, but then have links to all your sub Sitemaps.
Eric Enge: Another example is if you have pages on a site with content that from a user point of view you recognize that it's valuable to have the page, but you feel that is too duplicative of content on another page on the site
That page might still get links, but you don't want it in the Index and you want the crawler to follow the paths into the rest of the site.
Matt Cutts: That's right. Another good example is, maybe you have a login page, and everybody ends up linking to that login page. That provides very little content value, so you could NoIndex that page, but then the outgoing links would still have PageRank.
Now, if you want to you can also add a NoFollow metatag, and that will say don't show this page at all in Google's Index, and don't follow any outgoing links, and no PageRank flows from that page. We really think of these things as trying to provide as many opportunities as possible to sculpt where you want your PageRank to flow, or where you want Googlebot to spend more time and attention."
http://www.stonetemple.com/articles/interview-matt-cutts.shtml