Sometimes it is very helpful, although hard to read, the actual tax code and regulations. We appreciate Cornell Law School making it available online in as easy to find format.

This is the link for the US Tax Code in general which is Title 26
http://straylight.law.cornell.edu/uscode/html/uscode26/

Here is the link directly to Section 1031 of the Internal Revenue Code
http://straylight.law.cornell.edu/uscode/html/uscode26/usc_sec_26_00001031----000-.html

Here is the link to a free online resource “the Tax Almanac” that publishes the Treasury Regulations that interpret the code and become much of the actual law. These were established primarily in 1991 and have remained somewhat the same.
www.taxalmanac.org/index.php/Reg._1.1031(a)-1