Perhaps you should try some spelling variations:
"du hanh thiet so - hoc giao" » "du thanh thieu so - hoc giao", "du hanh theo so - hoc giao", "du hanh thieu so - hoc giao", "du hanh thuyet so - hoc giao", "du hanh thiet ke - hoc giao", "du hanh thiet so - hoc cao", "dieu hanh thiet so - hoc giao", "duy khanh thiet so - hoc giao", "luu hanh thiet so - hoc giao"
"vu manh tich su - don gian" » "vu mach tich su - don gian", "vu manh tinh su - don gian", "vu hanh thich su - don gian", "vu manh tich su - dan gian", "vu minh tich su - don gian", "vu anh tich su - don gian", "tu manh tich su - don gian", "vu manh lich su - don gian", "vu manh tich du - don gian", "vu manh tich so - don gian"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("vu manh tich su - don gian") or ("du hanh thiet so - hoc giao"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("vu manh tich su - don gian") OR ("du hanh thiet so - hoc giao")).
• Removing quotes may allow a broader search: (( vu manh tich su - don gian ) or ( du hanh thiet so - hoc giao )).
• Adding a wildcard symbol may retrieve word variants: (("vu manh tich su - don gian") or ("du hanh thiet so - hoc giao"))*.