Perhaps you should try some spelling variations:
thieu nghiem » thi nghiem, thu nghiem, thieu nhi
trinh khien » trinh thien, trinh nghien, trinh thiet
khien khien » thien nhien, thien chien, khien dien
canh trinh » canh tranh, hanh trinh, canh tinh
khien hoc » nhiet hoc, dien hoc
nghiem d » nghiem de, nghiem do, nghiem _
so canh » so sanh, bo canh, so danh
bo sach » co sach, hoc sach
d hoc » du hoc, ad hoc, de hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( so canh trinh khien khien hoc ) or ( bo sach thieu nghiem d hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( so canh trinh khien khien hoc ) OR ( bo sach thieu nghiem d hoc )).
• Adding a wildcard symbol may retrieve word variants: (( so canh trinh khien khien hoc ) or ( bo sach thieu nghiem d hoc ))*.