Perhaps you should try some spelling variations:
theo hanh » them thanh, thuc hanh, thi hanh
lam tinh » may tinh, ha tinh, ban tinh
tinh duc » minh duc, ninh duc, sinh duoc
dinh duc » minh duc, ninh duc, sinh duoc
heo van » theo van, ho van, hao van
van lam » van nam
vi dinh » vi sinh, vi tinh, vu dinh

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (( heo van lam tinh duc. ) OR ( theo hanh vi dinh duc. ))~.
• Adding a wildcard symbol may retrieve word variants: (( heo van lam tinh duc. ) or ( theo hanh vi dinh duc. ))*.