Perhaps you should try some spelling variations:
thanh dat » thanh hai, thanh van, thanh ha
sach duy » sach dung, sach duoc, sach dao
cham duc » pham duc, cham soc, pham duy
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
va cham » va chat, va tham
tang ma » mang may, tang van
nang ma » sang ma, nang cao, mang may
cua tre » cua te, cuu tre, cua triet

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