(1969). Communities: Student manual (Trial ed.). Science Curriculum Improvement Study.
Dyfyniad Arddull ChicagoCommunities: Student Manual. Trial ed. Berkeley, CA: Science Curriculum Improvement Study, 1969.
Dyfyniad MLACommunities: Student Manual. Trial ed. Science Curriculum Improvement Study, 1969.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.