Perhaps you should try some spelling variations:
sach tranh » canh tranh
thi nghiem » thuc nghiem
sach trac » sach truc, sach tham, sach tren
nghiem de » nghiem te, nghiem ve, nghiem dau
nghiem d » nghiem _, nghiem h, nghiem y
khac thi » khau thi, khuc thi, khuat thi
he khac » he khach, de khac, se khac
de hoc » te hoc, du hoc, dien hoc
d hoc » du hoc, ad hoc, y hoc

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 trac) or (sach tranh)) nghiem d hoc ) or ( he khac thi nghiem de hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu ((sach trac) OR (sach tranh)) nghiem d hoc ) OR ( he khac thi nghiem de hoc )).
• Adding a wildcard symbol may retrieve word variants: (( tu ((sach trac) or (sach tranh)) nghiem d hoc ) or ( he khac thi nghiem de hoc ))*.