Perhaps you should try some spelling variations:
cac truc » cau truc, cac tru, cac trung
hanh cua » manh cua, hang cua, hanh sua
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
truc va » thuc va, thuc vat, trung va
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
y nang » ky nang, ly nang, v nang

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 y nang ((le hoi) or (ma hoa)). hieu va cac truc va hanh cua ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((le hoi) OR (ma hoa)). hieu va cac truc va hanh cua ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang ((le hoi) or (ma hoa)). hieu va cac truc va hanh cua ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((le hoi) or (ma hoa)). hieu va cac truc va hanh cua ((cua tre) OR (cuu tre))*.