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.
Չիկագոյի ոճի (17րդ խմբ.) մեջբերումLuck, Lydia, Horst List, Gudrun Middell, and 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.
MLA (8րդ խմբ.) ՄեջբերումLuck, 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.