Perhaps you should try some spelling variations:
nghien cac » nghiep cach, nghien cuu, nghiep cay
cac khanh » cac thanh, cach nhanh, khac khanh
khanh hoa » thanh hoa, hang hoa
sach hoc » cach hoc, sach hoi, mach hoc
cac cong » cua cong
cong cac » cuong cac, cong tac, cong cau
gian dan » gian lang
toan tai » toan tap, doanh tai, toan ban
tu sach » thu sach, su sach, te sach
hoc xa » hoc ma

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 hoc tap, nghien cac cong cac khanh hoa hoc xa hoi va ((gian dan) or (toan tai))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach hoc tap, nghien cac cong cac khanh hoa hoc xa hoi va ((gian dan) OR (toan tai)).
• Adding a wildcard symbol may retrieve word variants: tu sach hoc tap, nghien cac cong cac khanh hoa hoc xa hoi va ((gian dan) or (toan tai))*.