Perhaps you should try some spelling variations:
khong thuoc » khang thuoc, hong phuoc, dong thuoc
khoan thanh » hoan thanh, phan thanh, hoang thanh
nghien huu » nghien cuu, nguyen huu, nhiem huu
toan khoan » toan khoa, toan phan, toan hoat
khong hoc » khung hoc, thong hoc, khong chuc
van thanh » ban thanh, van tuan
thanh dan » thanh san, thanh van, thanh dat
sach doi » sach hoi, sach moi, sach dao
huu toan » huu tuan, cuu toan, huy toan
hoi van » hoi va, hoi dan, hai van
doi tap » doi tac, doi dap, doi tai
tu sach » thu sach, su sach, te sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach doi tap, nghien huu toan khoan thanh ((khong hoc) or (khong thuoc)) xa hoi van thanh dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach doi tap, nghien huu toan khoan thanh ((khong hoc) OR (khong thuoc)) xa hoi van thanh dan.
• Adding a wildcard symbol may retrieve word variants: tu sach doi tap, nghien huu toan khoan thanh ((khong hoc) or (khong thuoc)) xa hoi van thanh dan*.