Perhaps you should try some spelling variations:
vat thanh » dat thanh, gat thanh, tat thanh
hieu van » hieu va, thien van, lieu va
vat hanh » van hanh, va hanh, nhat hanh
cau thuc » cau truc, cuu thuc, can thuc
van cau » van dau, van hau, van chat
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach ty, sach kem
vi cua » vai cua, di cua
x hoi » xa hoi, o hoi, x ho

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sach ky) or (sach y)) nang x hoi. hieu van cau thuc ((vat hanh) OR (vat thanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach ky) OR (sach y)) nang x hoi. hieu van cau thuc ((vat hanh) OR (vat thanh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach ky) or (sach y)) nang x hoi. hieu van cau thuc ((vat hanh) OR (vat thanh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach ky) or (sach y)) nang x hoi. hieu van cau thuc ((vat hanh) OR (vat thanh)) vi cua tre*.