Perhaps you should try some spelling variations:
thanh hai » thanh phan, thanh hoa, thanh san
thanh tai » thanh toan, doanh tai, thanh san
thu nang » thi nang, thu hang, thu bang
hieu van » thien van, lieu va, hieu ve
sach thu » sach thue, sach thieu, sach tham
cham cuu » cap cuu, chat cua
su sach » so sach, vu sach
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
cuu va » cuu van, cuu ve
ma hoi » mai hoi, xa hoi, ma hoa

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 thu nang ma hoi. ((hieu van) OR (hieu va)) cham cuu va ((thanh hai) or (thanh tai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach thu nang ma hoi. ((hieu van) OR (hieu va)) cham cuu va ((thanh hai) OR (thanh tai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach thu nang ma hoi. ((hieu van) OR (hieu va)) cham cuu va ((thanh hai) or (thanh tai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach thu nang ma hoi. ((hieu van) OR (hieu va)) cham cuu va ((thanh hai) or (thanh tai)) cua tre*.