Perhaps you should try some spelling variations:
tinh doi » trinh doc, trinh do, tinh hoc
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
cac duc » cac du, cao duc, cac dac
va tinh » may tinh
cua tre » cua te, cua triet, dua tren
cuu tre » cau tren, cau treo
y nang » ly nang, v nang, may nang
ve cac » va cac, vien cac

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