Perhaps you should try some spelling variations:
nghien huy » nghien cuu, nguyen huy, nghiep quy
huy toan » huy tran, huu toan, huy hoang
toan kho » toan khoa, toan ho, ton kho
kho khan » khoa kham, khoa than
khan hoa » khanh hoa, phan hoa, nhan hoa
nhan dan » phan dau, gian dan, nhan tai
tu mach » tu cach, tu manh, tu sach
tu hach » tu hanh, tu cach, tu sach
hoc xa » hoc ma
hoi ca » hoi cua, hoi cac, hoi cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu mach) or (tu hach)) hoc tap, nghien huy toan kho khan hoa hoc xa hoi ca nhan dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu mach) OR (tu hach)) hoc tap, nghien huy toan kho khan hoa hoc xa hoi ca nhan dan.
• Adding a wildcard symbol may retrieve word variants: ((tu mach) or (tu hach)) hoc tap, nghien huy toan kho khan hoa hoc xa hoi ca nhan dan*.