Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
dinh vai » dinh van, dinh vi, dinh va
tu sach » su sach, te sach, tu cach
hieu va » lieu va, hieu qua
vai cuu » vai cua
va dinh » van dinh, va kinh, va tinh
cam hoc » cao hoc, am hoc, cam hoa
cuu tre » cua tre, cau tren, cau treo
hieu ve » hieu van
dang xa » dang xay, lang xa, dang ha
ky dang » ky nang, ky danh

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