The series is divided into three main levels to support learners at every stage:

: The most advanced level, used globally for nearly 40 years to develop high-level language skills. Why It Is Highly Rated

The , co-authored by Betty S. Azar and Stacy A. Hagen , is widely considered the gold standard for English as a Second Language (ESL) instruction. Whether you are a student looking for self-study materials or a teacher seeking a structured classroom text, this series is highly recommended for its clarity and practical approach. Series Overview