Perhaps you should try some spelling variations:
pham thuc » phap thuc, pham chuc, nham thuc
sach thu » sach thue, sach thieu, sach tham
thanh va » thanh van, thanh ha, thanh ve
thuc day » thuc dan, thuc vat
su sach » so sach, vu sach
hanh va » hang va, hanh vi
va pham » van pham, va phat, va phap
hieu va » lieu va, hieu qua
tang ma » tang van
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: su sach thu ((tang ma) OR (mang may)) hoi. hieu va pham thuc day ((thanh va) or (hanh va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach thu ((tang ma) OR (mang may)) hoi. hieu va pham thuc day ((thanh va) OR (hanh va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach thu ((tang ma) OR (mang may)) hoi. hieu va pham thuc day ((thanh va) or (hanh va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach thu ((tang ma) OR (mang may)) hoi. hieu va pham thuc day ((thanh va) or (hanh va)) cua tre*.