Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
cua cau » cua cac, cua chu, cua can
vuc van » duc van, luc van, thuc van
cac vuc » cac nuoc, cac vung, cac cuoc
hieu ve » hieu va, hieu van
cho hoc » co hoc, khoa hoc
ty hang » ly hang, thi hang, thu hang
cua cay » cua cac
ve cac » va cac, vien cac

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ty hang) OR (ty xang)) cho hoc. hieu ve cac vuc van hanh vi ((cua cau) OR (cua cay))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((ty hang) or (ty xang)) cho hoc. hieu ve cac vuc van hanh vi ((cua cau) OR (cua cay))~".
• Adding a wildcard symbol may retrieve word variants: toc sach ((ty hang) or (ty xang)) cho hoc. hieu ve cac vuc van hanh vi ((cua cau) OR (cua cay))*.