Perhaps you should try some spelling variations:
thuat sach » thuat lanh, thuat san
sach nay » sach hay, sach vay, sach nang
tinh va » tich va, trinh van, trinh vat
va tinh » may tinh
cau duc » cao duc, cau luc, chu duc
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu van
long ha » dong ha, cong ha, dong hoa
va cua » va chua, via cua, ca cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thuat sach nay ((lang ha) OR (long ha)) hoi. ((hieu ve) or (hieu va)) cau duc va tinh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thuat sach nay ((lang ha) OR (long ha)) hoi. ((hieu ve) OR (hieu va)) cau duc va tinh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thuat sach nay ((lang ha) OR (long ha)) hoi. ((hieu ve) or (hieu va)) cau duc va tinh va cua tre".
• Adding a wildcard symbol may retrieve word variants: thuat sach nay ((lang ha) OR (long ha)) hoi. ((hieu ve) or (hieu va)) cau duc va tinh va cua tre*.