Perhaps you should try some spelling variations:
sach doi » sach hoi, sach moi, sach dao
khoa hoc » hoa hoc
cau cham » ca cham, cau chan, cau chap
cham van » pham van, cham va, chao van
tu sach » thu sach, su sach, te sach
doi tac » dong tac
cuu mon » cuu mo, cuu mot, cuu cong
hoi cau » hoi chu, hoc cau, hoa cau
hoc da » hoc dai, hoc dat, hoc dao
hoc xa » hoc ma

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach doi tac, nghien cuu mon ((hoc da) OR (hoc dan)) khoa hoc xa hoi cau cham van~.
• Adding a wildcard symbol may retrieve word variants: tu sach doi tac, nghien cuu mon ((hoc da) or (hoc dan)) khoa hoc xa hoi cau cham van*.