Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
thu sach » thuat sach, thuoc sach, thu hoach
danh vai » danh sai, danh va, doanh van
tu sach » su sach, te sach, tu cach
vai cua » dai cua, hai cua, lai cua
va danh » va dinh, va dan, va hanh
cac loc » cac lop, cac toc, cac 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
loc va » hoc va, luc va

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (thu sach)) ky nang ma hoi. ((hieu ve) OR (hieu van)) cac loc va danh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (thu sach)) ky nang ma hoi. ((hieu ve) OR (hieu van)) cac loc va danh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (thu sach)) ky nang ma hoi. ((hieu ve) OR (hieu van)) cac loc va danh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (thu sach)) ky nang ma hoi. ((hieu ve) OR (hieu van)) cac loc va danh vai cua tre*.