Perhaps you should try some spelling variations:
cach thuc » anh thuc, cac thu
hieu van » hieu va, thien van, lieu va
cac thuc » cac thu, can thuc, cay thuc
va hanh » van hanh, va thanh, va danh
vu sach » vu bach, vu khach
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
su sach » so sach
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua

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

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