Perhaps you should try some spelling variations:
sach thi » sach thu, sach tai, sach thieu
thi nang » thi cong, ki nang, thi hanh
van hanh » van thanh, ban hanh, van anh
vu sach » vu bach, su sach, vu khach
vuc van » duc van, luc van, thuc van
va chat » van chat, va phat, hoa chat
ca viet » va viet, co viet, hoa viet
ve cam » ve cham, ve cac, va cam
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai
vi ca » vit ca, li ca, va ca

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 thi nang o hoi. hieu ((ve cam) or (((va chat) OR (cao chat)))) vuc van hanh vi ca viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach thi nang o hoi. hieu ((ve cam) OR (((va chat) OR (cao chat)))) vuc van hanh vi ca viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach thi nang o hoi. hieu ((ve cam) or (((va chat) OR (cao chat)))) vuc van hanh vi ca viet".
• Adding a wildcard symbol may retrieve word variants: vu sach thi nang o hoi. hieu ((ve cam) or (((va chat) OR (cao chat)))) vuc van hanh vi ca viet*.