Perhaps you should try some spelling variations:
sach doi » sach hoi, sach moi, sach dao
cua ngan » cua ban, cua dan
tu sach » thu sach, su sach, te sach
doi tap » doi tac, doi dap, doi tai
cuu mon » cuu mo, cuu mot, cuu cong
mon hoa » mon hoc, dong hoa, cong hoa
dan hoa » danh hoa, dan hoat, dan khoa
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 doi tap, nghien cuu mon hoa dan hoa hoc xa hoi ((cua ngan) or (vu ngan)) dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach doi tap, nghien cuu mon hoa dan hoa hoc xa hoi ((cua ngan) OR (vu ngan)) dan.
• Adding a wildcard symbol may retrieve word variants: tu sach doi tap, nghien cuu mon hoa dan hoa hoc xa hoi ((cua ngan) or (vu ngan)) dan*.