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, 21 (4). Retrieved from http://scholarworks.wmich.edu/reading_horizons/vol21/iss4/10