Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
nang tai » hang tai, tang tai, sang tai
tai khoa » da khoa, noi khoa
va hanh » van hanh, va thanh, va danh
cam luc » cam xuc, cau luc
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach kem
sach ty » sach y, sach tu, sach thu
cua tre » cua te, cuu tre, cua triet
luc va » duc va, tuc va, loc va
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: so ((sach ky) OR (sach ty)) nang tai khoa. ((hieu van) or (hieu va)) cam luc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ky) OR (sach ty)) nang tai khoa. ((hieu van) OR (hieu va)) cam luc va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach ky) OR (sach ty)) nang tai khoa. ((hieu van) or (hieu va)) cam luc va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: so ((sach ky) OR (sach ty)) nang tai khoa. ((hieu van) or (hieu va)) cam luc va hanh vi cua tre*.