do5 doesn't invent a way to rank your day. It applies three ideas that were already well understood — and does the tedious part for you, every night. Each is explained here with its sources.
Urgent is not the same as important. The two-question sort from 1954, why important-but-not-urgent outranks urgent noise, and how do5 orders tasks with it.
Pareto's observation, Juran's "vital few," and why a hard cap of three goal-traced priorities does what no calculation can.
Specific, Measurable, Achievable, Relevant, Timely — from Doran (1981) to Harvard Health, and how do5's coach refuses a goal without a finish line.