Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
hanh doi » thanh doi, hanh noi, hang doi
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va
va hanh » van hanh, va thanh, va danh
doi cuu » doi cua, doi cuoc
cuu tre » cua tre, cau tren, cau treo
nuoc » quoc, duoc, ngoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) or (toc sach)) ky nang ma hoa. ((hieu ve) OR (hieu van)) dat nuoc va hanh doi cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky nang ma hoa. ((hieu ve) OR (hieu van)) dat nuoc va hanh doi cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (toc sach)) ky nang ma hoa. ((hieu ve) OR (hieu van)) dat nuoc va hanh doi cuu tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) ky nang ma hoa. ((hieu ve) OR (hieu van)) dat nuoc va hanh doi cuu tre*.