Perhaps you should try some spelling variations:
thieu sach » chieu sach, thien hach, hieu cach
hoc thieu » toc thieu, hoc hien
lanh manh » lanh tranh, lan anh, van manh
cua trong » cua truong, cua trung, qua trong
van hanh » van thanh, ban hanh, van anh
san toan » van toan, dan toan, manh toan
dan than » dan chan, ban than, van than

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: hoc thieu sach - ((lanh manh) OR (van hanh)) cua trong cong ((san toan) OR (dan than)) cao~.
• Adding a wildcard symbol may retrieve word variants: hoc thieu sach - ((lanh manh) or (van hanh)) cua trong cong ((san toan) or (dan than)) cao*.