Luck, L., List, H., Middell, G., & Hybler, Z. (1990). English step by step: English for beginners and an elementary refresher course, English for intermediate learners, English for advanced learners and scientiests (8., unveränd. Aufl.). Verlag Enzyklopädie.
Trích dẫn kiểu Chicago (xuất bản lần thứ 7)Luck, Lydia, Horst List, Gudrun Middell, và Zdenek Hybler. English Step by Step: English for Beginners and an Elementary Refresher Course, English for Intermediate Learners, English for Advanced Learners and Scientiests. 8., unveränd. Aufl. Leipzig: Verlag Enzyklopädie, 1990.
Trích dẫn kiểu MLA (xuất bản lần thứ 8)Luck, Lydia, et al. English Step by Step: English for Beginners and an Elementary Refresher Course, English for Intermediate Learners, English for Advanced Learners and Scientiests. 8., unveränd. Aufl. Verlag Enzyklopädie, 1990.