Perhaps you should try some spelling variations:
thiet hach » thien hach, thuyet hach, thiet hai
thong cong » trong cong, tong cong, thong thong
hoc thiet » hoc thieu, hoc thuyet, hoc hien
hanh tang » hanh trang, anh tang, hanh tung
hanh mang » nhanh mang, hanh trang, nhanh lang
dung cong » dung trong
dan toan » van toan, dan than, manh toan
toan ban » van ban

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc thiet hach - ((hanh tang) or (hanh mang)) cua ((thong cong) or (dung cong)) dan toan ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc thiet hach - ((hanh tang) OR (hanh mang)) cua ((thong cong) OR (dung cong)) dan toan ban.
• Adding a wildcard symbol may retrieve word variants: hoc thiet hach - ((hanh tang) or (hanh mang)) cua ((thong cong) or (dung cong)) dan toan ban*.