Perhaps you should try some spelling variations:
sach thue » sach thu, sach thieu, sach tham
thue nang » thien nang, thuat nang, thi nang
van hanh » van thanh, ban hanh, van anh
vu sach » vu bach, su sach, vu khach
ca viet » co viet, hoa viet, san viet
duc van » duc va, duc tan, duc manh
va viet » hoa viet, san viet, mai viet
va cam » va cham, va cac, va cao
ve cam » ve cham, ve cac, ve cai
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach thue nang o hoi. hieu ((ve cam) or (va cam)) duc van hanh vi ((ca viet) or (va viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach thue nang o hoi. hieu ((ve cam) OR (va cam)) duc van hanh vi ((ca viet) OR (va viet)).
• Adding a wildcard symbol may retrieve word variants: vu sach thue nang o hoi. hieu ((ve cam) or (va cam)) duc van hanh vi ((ca viet) or (va viet))*.