Perhaps you should try some spelling variations:
thanh vai » thanh hai, thanh van, thanh tai
tan thanh » tran thanh, tang thanh, toan thanh
hieu van » hieu va, thien van, lieu va
cua viet » ca viet, hoa viet, cua vat
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
ty hang » ly hang, ty xang, thi hang
hang ca » hang va, nang cao, hang tai
van cau » van dau, van hau, van chat
cau duc » cao duc, cau luc, chu duc
cua tre » cua te, cuu tre, cua triet
ca hoi » cau hoi, cua hoi, xa hoi

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 hang ca hoi. hieu van cau duc tan thanh vai ((cua tre) or (cua viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty hang ca hoi. hieu van cau duc tan thanh vai ((cua tre) OR (cua viet)).
• Adding a wildcard symbol may retrieve word variants: su sach ty hang ca hoi. hieu van cau duc tan thanh vai ((cua tre) or (cua viet))*.