Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
tinh vai » tinh va, tinh hai, tinh bai
lang van » dang van, tang van, hoang van
tu sach » thu sach, su sach, te sach
ca viet » co viet, hoa viet, san viet
va tinh » may tinh
cam duc » cam xuc, cao duc, pham duc
hieu vu » hieu va, hieu ve, hieu su
van hoi » van hoa, van hoc, van hoe
ky lang » ky nang, ky dang, ky tang
va viet » hoa viet, san viet, mai viet
vu cam » vu cham, vu cao, va cam

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 (doc sach)) ky lang van hoi. hieu vu cam duc va tinh vai ((ca viet) OR (va viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (doc sach)) ky lang van hoi. hieu vu cam duc va tinh vai ((ca viet) OR (va viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (doc sach)) ky lang van hoi. hieu vu cam duc va tinh vai ((ca viet) OR (va viet))".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (doc sach)) ky lang van hoi. hieu vu cam duc va tinh vai ((ca viet) OR (va viet))*.