Very interesting. Below are a couple of links to top pieces on the scope triangle, search appreciated.
A Project Management Primer: Basic Principles – Scope Triangle
The “Broken Iron Triangle” Software Development Anti-pattern
Phi Beta Iota: The Scope Triangle is desperately out of date. The two new major factors are first: the role that intelligence (decision-support) can play in what we have called since the 1990's “Information Arbitrage,” which is the use of information converted into intelligence as a substitute for time, space, capital, and labor as well as materials (e.g. substituting plastic for steel in car construction); and second: the role that social production or Collective Intelligence can play in being a substitute for hard and soft power–for example, Thomas Jefferson's observation that a Nation's best defense was an educated (armed) citizenry.