Perhaps you should try some spelling variations:
vat thanh » dat thanh, gat thanh, tat thanh
vat hanh » van hanh, va hanh, nhat hanh
cau thuc » cau truc, cuu thuc, can thuc
tu sach » thu sach, su sach, tu cach
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
te sach » toc sach
vi cua » vai cua, di cua
ve cau » ke cau, va cau, ve cac

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) or (te sach)) ky lang xa hoi. hieu ve cau thuc ((vat hanh) OR (vat thanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (te sach)) ky lang xa hoi. hieu ve cau thuc ((vat hanh) OR (vat thanh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (te sach)) ky lang xa hoi. hieu ve cau thuc ((vat hanh) OR (vat thanh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (te sach)) ky lang xa hoi. hieu ve cau thuc ((vat hanh) OR (vat thanh)) vi cua tre*.