Perhaps you should try some spelling variations:
trinh viet » ninh viet, trinh vat
viet cua » viec cua, viet ca, viet qua
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
ty tang » tay tang, ty xang, ty hang
tang ma » mang may, tang van
hieu va » lieu va
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa
tuc va » thuc va, truc va, tuc xa

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 ty tang ma hoi. ((hieu va) OR (hieu qua)) coc ((tuc va) or (duc va)) trinh viet cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty tang ma hoi. ((hieu va) OR (hieu qua)) coc ((tuc va) OR (duc va)) trinh viet cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty tang ma hoi. ((hieu va) OR (hieu qua)) coc ((tuc va) or (duc va)) trinh viet cua tre*".