Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
cua viet » ca viet, hoa viet, cua vat
sach ky » sach y, sach ty, sach kem
hieu ve » hieu va, hieu van
ve pham » vi pham, v pham, ve phan
va hanh » van hanh, va thanh, va danh
hanh di » hanh vi, hanh de, hang di
sac ky » cac ky, sai ky
x hoi » xa hoi, o hoi, x ho

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 ky) OR (sac ky)) nang x hoi. hieu ve pham duc va hanh di ((cau tren) or (cua viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach ky) OR (sac ky)) nang x hoi. hieu ve pham duc va hanh di ((cau tren) OR (cua viet))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach ky) OR (sac ky)) nang x hoi. hieu ve pham duc va hanh di ((cau tren) or (cua viet))*".