Perhaps you should try some spelling variations:
trinh di » trinh do, trinh dien, trinh dinh
va trinh » van trinh, va tinh, lap trinh
cua tre » cua te, cua triet, dua tren
sach ty » sach y, sach thu, xach tay
hieu va » lieu va, hieu qua
sach tu » sach thu, cach tu, sach uu
cuu tre » cau tren, cau treo
x hoi » xa hoi, o hoi, x ho
du va » dau va, tu va, su va

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sach ty) or (sach tu)) nang x hoi. hieu va cac du va trinh di ((cua tre) OR (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach ty) OR (sach tu)) nang x hoi. hieu va cac du va trinh di ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach ty) or (sach tu)) nang x hoi. hieu va cac du va trinh di ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: thu ((sach ty) or (sach tu)) nang x hoi. hieu va cac du va trinh di ((cua tre) OR (cuu tre))*.