Perhaps you should try some spelling variations:
day hanh » day nhanh, day thanh, dao hanh
thuc day » thuc dan, thuc vat
nam thuc » nam thuoc, am thuc, nam thu
lang van » dang van, hoang van, giang van
tang van » dang van, hoang van, trong van
hieu va » lieu va, hieu qua
sach ky » sac ky, sach ty, sach kem
cua tre » cua te, cuu tre, cua triet
va nam » van nam, ha nam, va nay
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 ky) OR (sach y)) ((lang van) or (tang van)) hoi. hieu va nam thuc day hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu ((sach ky) OR (sach y)) ((lang van) OR (tang van)) hoi. hieu va nam thuc day hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu ((sach ky) OR (sach y)) ((lang van) or (tang van)) hoi. hieu va nam thuc day hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: vu ((sach ky) OR (sach y)) ((lang van) or (tang van)) hoi. hieu va nam thuc day hanh vi cua tre*.