Galili, Igal (1993). "Weight and gravity: teachers' ambiguity and students' confusion about the concepts". International Journal of Science Education. 15 (2): 149–162. Bibcode:1993IJSEd..15..149G. doi:10.1080/0950069930150204.
Galili, Igal (1993). "Weight and gravity: teachers' ambiguity and students' confusion about the concepts". International Journal of Science Education. 15 (2): 149–162. Bibcode:1993IJSEd..15..149G. doi:10.1080/0950069930150204.