Perhaps you should try some spelling variations:
thiet hach » thien hach, thuyet hach, thiet hai
hoc thiet » hoc thieu, hoc thuyet, hoc hien
hanh tran » hanh trang, thanh tran, hanh tram
bang cong » dang cong, bang song, hang cong
tran van » luan van
van bang » van ban, van nang, von bang
van quan » van ban
van tan » van tuan, van ban, van tai

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 thiet hach - hanh tran van bang cong ((van quan) OR (van tan)) cau~.
• Adding a wildcard symbol may retrieve word variants: hoc thiet hach - hanh tran van bang cong ((van quan) or (van tan)) cau*.