Perhaps you should try some spelling variations:
sach nay » sach hay, sach vay, sach nang
sach tay » xach tay, sach hay, sach tai
va hanh » van hanh, va thanh, va danh
hau luc » hau loc, cau luc, nhan luc
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
tang ha » lang ha, tang ma, trung ha
ha hoi » hoa hoi, ha noi, xa hoi
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: tu ((sach tay) OR (sach nay)) tang ha hoi. ((hieu ve) or (hieu qua)) hau luc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach tay) OR (sach nay)) tang ha hoi. ((hieu ve) OR (hieu qua)) hau luc va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach tay) OR (sach nay)) tang ha hoi. ((hieu ve) or (hieu qua)) hau luc va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach tay) OR (sach nay)) tang ha hoi. ((hieu ve) or (hieu qua)) hau luc va hanh vi cua tre*.