# A critical evaluation of text difficulty development in ELT textbook series: A corpus-based approach using variability neighbor clustering

> Research article (System, 2016) · cited 53× · AI/ML

**Wikidata**: [openalex:W2326539347](https://www.wikidata.org/wiki/openalex:W2326539347)  
**Source**: https://4ort.xyz/entity/a-critical-evaluation-of-text-difficulty-development-in-elt-textbook-series-a-corpus-based-approach-using-variability-ne