The impact of the teaching learning process on independent study by private university students in Central Java and Yogyakarta : development of the research instrument, Yogyakarta, 1991 (Joint research project Universitas Kristen Satya Wacana, Universitas Muhammadiyah, Surakarta, IKIP Sanata Dharma, Yogyakarta and Konrad Adenauer Stif[t]ung, 1991)