Poland ; Evaluation criterion (language teaching) ; DaF; Deutsch als Zweitsprache; German as a second language; DaZ; German as a foreign language ; English as a second language; ESL; TESOL ; Textbook analysis ; Sampling; Language corpus; Sprachkorpus; Datensammlung; Data collection; Textkorpus (method.) ; Text corpus (method.) ; Corpus linguistics ; BNC ; German ; English