Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
hanh ca » hanh cac, hanh cat, hanh cua
va hanh » van hanh, va thanh, va danh
cac bac » cac bai, cac ban, cac cach
cac tac » cac toc, cac dac, cac tai
cuu tre » cua tre, cau tren, cau treo
y nang » ky nang, ly nang, v nang
ma hoi » mai hoi, xa hoi, me hoi
ca cuu » cap cuu, cua cuu, 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: tu sach y nang ((ma hoi) or (ma hoa)). hieu qua ((cac tac) OR (cac bac)) va hanh ca cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((ma hoi) OR (ma hoa)). hieu qua ((cac tac) OR (cac bac)) va hanh ca cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang ((ma hoi) or (ma hoa)). hieu qua ((cac tac) OR (cac bac)) va hanh ca cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((ma hoi) or (ma hoa)). hieu qua ((cac tac) OR (cac bac)) va hanh ca cuu tre*.