The Theory of Constraints is the creation of Eliyahu M. Goldratt first introduced in his book The Goal.  TOC claims that within any system, there is a choke point (constraint) which determines the throughput of the system, whether that throughput is units of production, profits, etc.  What sets TOC apart from other research is it provides a solution!  TOC includes tools to identify constraints and manage those constraints to maximize throughput.  Most of the current published works focus on production just as six-sigma, TQM, and similar methods do.  The application is much broader, and newer books are expanding TOC into the other realms, like human resource management.

The Goal is actually written as a novel.  Unfortunately, it doesn’t present enough of the solution.