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

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