1. Measuring incremental changes in world knowledge- Frishkoff et al..pdf
2. ATOS - ATOS (Renaissance Learning)
   1. ATOS Reading_level_correlations.pdf
   2. ATOS Reading Levels Comparison Chart.htm
   3. ReadabilityComparisonArticle_ATOS advantages.pdf
3. DRP - Degrees of Reading Power (Questar)
4. FK - Flesch Kincaid
5. Lexile - Lexile Framework
   1. Lexile-Reading-Measurement-and-Success-0504_MetaMetricsWhitepaper.pdf
   2. SRI_ProfPaper_Lexiles.pdf
6. SR - Source Rater ( Educational Testing Service)
7. RM - Pearson Reading Maturity Metric (Pearson Education)
   1. RM PearsonsTextComplexity.pdf