View the code for an operating system that makes use of protected mode programming. A good source for information. This has sample
code illustrating concepts discussed in this site, as well as more advanced concepts such as interrupt implementation.
Intel's 80386 reference manual. Documentation straight from intel. Contains painstaking detail on advanced protected mode
features, many of which are beyond the scope of this site. You can also find details about every Intel-supported assembly
instruction in the site's appendix.