Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
hieu van » hieu va, thien van, lieu va
te sach » toc sach
danh vi » hanh vi, dinh vi, danh di
va danh » va dinh, va dan, va hanh
cac hoc » cach hoc, cac hop, bac hoc
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va
nang ma » tang ma, sang ma, nang cao
ma hoi » mai hoi, xa hoi, ma hoa
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: ((te sach) or (thuat sach)) ky nang ma hoi. ((hieu ve) OR (hieu van)) cac hoc va danh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (thuat sach)) ky nang ma hoi. ((hieu ve) OR (hieu van)) cac hoc va danh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (thuat sach)) ky nang ma hoi. ((hieu ve) OR (hieu van)) cac hoc va danh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (thuat sach)) ky nang ma hoi. ((hieu ve) OR (hieu van)) cac hoc va danh vi cua tre*.