Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
nam buoc » nam duoc, nam quoc, nam thuoc
nam luoc » nam duoc, nam quoc, nam thuoc
sach ky » sach y, sach ty, sach kem
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
cao hoi » cau hoi, co hoi, cao hoc
sac ky » cac ky, sai ky
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: te ((sach ky) or (sac ky)) nang cao hoi. hieu va ((nam luoc) OR (nam buoc)) van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach ky) OR (sac ky)) nang cao hoi. hieu va ((nam luoc) OR (nam buoc)) van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach ky) or (sac ky)) nang cao hoi. hieu va ((nam luoc) OR (nam buoc)) van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: te ((sach ky) or (sac ky)) nang cao hoi. hieu va ((nam luoc) OR (nam buoc)) van hanh vi cua tre*.