Perhaps you should try some spelling variations:
khoan hoi » khoan nhoi, khoa hoi, khoa hoc
khac hoi » khac tuoi, phuc hoi, khac hau
mach hoc » cach hoc, dich hoc, anh hoc
minh dao » minh danh, minh giao, lanh dao
su mach » su sach
hoc hoa » hoc khoa
vu minh » vu dinh, van minh
dao hoa » dao hoan, do hoa, dao ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( su mach hoc hoa ) or ((( vu ((khac hoi) OR (khoan hoi)) ha ) or ( vu minh dao hoa ))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( su mach hoc hoa ) OR ((( vu ((khac hoi) OR (khoan hoi)) ha ) OR ( vu minh dao hoa )))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( su mach hoc hoa ) or ((( vu ((khac hoi) OR (khoan hoi)) ha ) or ( vu minh dao hoa ))))".
• Adding a wildcard symbol may retrieve word variants: (( su mach hoc hoa ) or ((( vu ((khac hoi) OR (khoan hoi)) ha ) or ( vu minh dao hoa ))))*.