Levelt, Willem J. M. Language Production Group Levelt, MPI for Psycholinguistics, Max Planck Society;
Levelt_Skill_theory_SSLA_1978.pdf (Any fulltext), 912KB
Levelt, W. J. M. (1978). Skill theory and language teaching. Studies in Second Language Acquisition, 1(1), 53-70. doi:10.1017/S0272263100000711.