Perhaps you should try some spelling variations:
"vu mach tich so - toan giao" » "vu mach tich so - ton giao", "vu mach tich so - toan cao", "vu mach tich so - hoa giao", "vi mach tich so - toan giao", "vu bach tich so - toan giao", "vu manh tich so - toan giao", "vu mach tich bao - toan giao", "vu mach tinh son - toan giao"
"tu hanh tinh so - don gian" » "tu hanh trinh so - don gian", "tu nhanh tinh so - don gian", "tu thanh tinh so - don gian", "tu hanh tinh so - dan gian", "du hanh tinh so - don gian", "lu hanh tinh so - don gian", "thuc hanh tinh so - don gian", "tu hanh tinh son - don gian", "tu hanh tinh soc - don gian", "tu hanh dinh 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 mach tich so - toan giao") or ("tu hanh tinh so - don gian"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("vu mach tich so - toan giao") OR ("tu hanh tinh so - don gian"))*.
• Removing quotes may allow a broader search: (( vu mach tich so - toan giao ) or ( tu hanh tinh so - don gian ))*.