I don't have the link but go to Wexler's and he has a page on Doubled Dies and the various types of doubling. It's good.
Wexler doesn't list Jefferson varieties (for the OP's future reference), but this gentleman does... https://www2.briansvarietycoins.com// And here are the pages of which you speak... http://doubleddie.com/144801.html http://doubleddie.com/58222.html
Brian Ribar does the nickel errors and varieties. His name and address/email contacts are on John Wexler's site under "Coin Examinations" on the left of the landing page at the very top.
For the record, I never said Wexler has nickel varieties. I said his website has an article on the types of doubling found on coins. He explains very well, what a Doubled Die is. The article covers all denominations.
And is why I specifically addressed the fact I was clarifying for the OP's sake while providing the suggested links for his convenience. Just for the record, of course...