Perhaps you should try some spelling variations:
thien van » thi van
sach nuoc » sach duoc, cac nuoc, bach tuoc
hieu viec » nhieu viec, hieu ve, sieu viet
su sach » so sach, vu sach
doi cua » dai cua, hoi cua
dan doi » dan hoi, dan toi, van doi
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
sang ma » tang ma, sang tao, mang may
nang ma » tang ma, nang cao, mang may
va dan » ca dan, va dao, va dau

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

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