Perhaps you should try some spelling variations:
cach thoi » cac thoi, cach thuc, cach noi
hang khoa » dung khoa
thoi tap » toi tap, hoc tap, thoi dai
cuu cong » cua cong, thu cong, cac cong
cong coc » cong cuoc, cong cac, cong co
coc hang » hoc hang, oc hang, moc hoang
khoa hoc » hoa hoc
phan van » pham van, thanh van, luan van
su cach » su sach, tu cach, su cac
hoi van » hoi va, hai van, hoi han
hoi dan » hoa dan, hoc dan, hoi dap

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

• Performing a fuzzy search may retrieve terms with similar spellings: su cach thoi tap, nghien cuu cong coc hang khoa hoc ma ((hoi van) OR (hoi dan)) phan van~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su cach thoi tap, nghien cuu cong coc hang khoa hoc ma ((hoi van) OR (hoi dan)) phan van".
• Adding a wildcard symbol may retrieve word variants: su cach thoi tap, nghien cuu cong coc hang khoa hoc ma ((hoi van) OR (hoi dan)) phan van*.