Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
lanh hai » manh hai, thanh hai, lang chai
quoc ban » quoc bao, quoc lan, quoc quan
danh hai » dang hai, manh hai, danh hau
cua tre » cua te, cuu tre, cua triet
duc van » duc va, duc tan, duc manh
van lam » van nam
tang xa » trang xa, tang ma, lang xa
y tang » ky tang, 6 tang, 7 tang

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach y tang xa hoi. hieu van lam ((quoc ban) or (duc van)) ((danh hai) OR (lanh hai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y tang xa hoi. hieu van lam ((quoc ban) OR (duc van)) ((danh hai) OR (lanh hai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach y tang xa hoi. hieu van lam ((quoc ban) or (duc van)) ((danh hai) OR (lanh hai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: thu sach y tang xa hoi. hieu van lam ((quoc ban) or (duc van)) ((danh hai) OR (lanh hai)) cua tre*.