Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
ty hang » ly hang, thi hang, thu hang
cho hoc » co hoc, khoa hoc
qua cac » cua cac
cac luc » cau luc, coc luc, cac nuoc
luc van » luoc van, luu van, duc van
cua cau » cua cac, cua chu, cua can
cua cay » cua cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ((ty hang) or (ty xang)) cho hoc. hieu qua cac luc van hanh vi ((cua cau) OR (cua cay))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ty hang) OR (ty xang)) cho hoc. hieu qua cac luc 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 qua cac luc van hanh vi ((cua cau) OR (cua cay))*".