One of the many problems facing educators involved in instructional programming is how to tell whether a given piece of material is likely to be readable to an individual child.
Harber, J. R. (1981). The Importance of Evaluating the Syntactic Complexity of Instructional Material. Reading Horizons: A Journal of Literacy and Language Arts, 21 (4). Retrieved from https://scholarworks.wmich.edu/reading_horizons/vol21/iss4/10