For UK chart positions I have used those published throughout the 1960s in the trade weekly Record Retailer; these charts can now be found at The charts published in the weekly paper New Musical Express (NME) were based on a larger sample of returns from shops, so in theory ought to be more representative of actual sales across the country.  On the down side, though, they only had thirty chart positions as against Record Retailer's forty; so "One of Us Must Know", for example, which got to No.33 in the Record Retailer chart, didn't appear in NME's chart at all.*  For the majority of Dylan singles that did appear in both charts, there is generally not a great deal of difference in practice; any significant exceptions are mentioned in the text.

For US chart positions I have used the "Hot 100" singles charts published every week in Billboard, as these seem to be the most widely-quoted.

* The New Musical Express charts are to be found in the book 40 Years of NME Charts by Daffyd Rees, Barry Lazell & Roger Osborne (Boxtree, 1992).