Early Number Skill
A course for parents of 3 to 5 year-olds.
Online course.
Workbooks by Sanjay Raghav, with graphics by Vishnu.
How to teach number concept.
Language and conceptual schema of number.
Concept + additive reasoning
Proportional Reasoning Group
If have language + number concept + proportional reasoning --> advance to Algebraic Reasoning Group
Conceptually 5-year-olds