Perhaps you should try some spelling variations:
lam trung » lam truong, nam trung, lap trung
lam trong » lam truong, nam trong, la trong
sach hay » sach han, sach ha, sach nay
hieu van » hieu va, thien van, lieu va
va hanh » van hanh, va thanh, va danh
lang xa » lang ha, dang xay, lang van
sach ty » sach y, sach tu, sach thu
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: su ((sach hay) or (sach ty)) lang xa hoi. hieu van ((lam trung) OR (lam trong)) va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach hay) OR (sach ty)) lang xa hoi. hieu van ((lam trung) OR (lam trong)) va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach hay) or (sach ty)) lang xa hoi. hieu van ((lam trung) OR (lam trong)) va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su ((sach hay) or (sach ty)) lang xa hoi. hieu van ((lam trung) OR (lam trong)) va hanh vi cua tre*.