Perhaps you should try some spelling variations:
thanh hang » thanh hoang, thanh thang, tranh hang
nghien cac » nghiep cach, nghien cuu, nghiep cay
hang dich » hoang dinh, van dich, ban dich
hoa thanh » hoan thanh, ha thanh, hoc thanh
dich can » dich han, dich ran, lich can
sach hoc » cach hoc, sach hoi, mach hoc
cong hoa » dong hoa, dong hoc, hang hoa
cac cong » cua cong
can hoi » cau hoi, can ho, dan hoi
ca giao » cua giao, co giao, c giao
va giao » van giao, va giai, va gia
so sach » so sanh, bo sach, co sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach hoc tap, nghien cac cong hoa thanh hang dich can hoi ((ca giao) or (va giao)) dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach hoc tap, nghien cac cong hoa thanh hang dich can hoi ((ca giao) OR (va giao)) dan.
• Adding a wildcard symbol may retrieve word variants: so sach hoc tap, nghien cac cong hoa thanh hang dich can hoi ((ca giao) or (va giao)) dan*.