How can I see the revision history of a particular FAR? For instance, I don't remember paragraph 61.51(e)(iii) at all from way back when I studied it to determine when I could log PIC time.  I'm fairly certain that it has been added since then (actually, there was no sport pilot license back then so I know that it has at least been changed), but I would like to know when it was changed and what the changes were.
At the bottom of the reg, it includes this:

[Doc. No. 25910, 62 FR 16298, Apr. 4, 1997; Amdt. 61-103, 62 FR 40897,
July 30, 1997; Amdt. 61-104, 63 FR 20286, Apr. 23, 1998; Amdt. 61-110,
69 FR 44865, July 27, 2004; Amdt. 61-124, 74 FR 42549, Aug. 21, 2009;
Amdt. 61-128, 76 FR 54105, Aug. 31, 2011]

This tells me when it was amended, but not what was amended.
Does the FAA make that information available?
Changes to federal aviation regulations are listed on the FAA’s Regulatory &amp; Guidance Library (RGL) at http://rgl.faa.gov/:


From the home page, click on the database titled "Code of Federal Regulations"
On the left, in the navigation tree, select one of the branches under "Historical CFR" (for example, "By Part")
On the right, expand the items leading to the regulation that you are looking for (in this case Part 61)
Scroll down to the regulation that you are looking for (61.51) and it will list the original version and all of the revisions:




Each revision is a link which takes you to the regulation as of that version, with links to the NPRM's and dockets so that you can see what has been changed!