Perhaps you should try some spelling variations:
hieu luc » hieu luat, hieu qua
su sach » so sach, vu sach
te sach » toc sach
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
va tinh » may tinh
tinh di » tinh doi, trinh di, tinh da
cua tre » cua te, cuu tre, cua triet
cua va » cua vat, chua va, cua van
di cua » dai cua, doi cua, de cua
nhat » nhan

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) or (te sach)) ky lang xa hoi. hieu luc nhat cua va tinh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (te sach)) ky lang xa hoi. hieu luc nhat cua va tinh di cua tre.
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (te sach)) ky lang xa hoi. hieu luc nhat cua va tinh di cua tre*.