Perhaps you should try some spelling variations:
ngoc dang » ngoc dung, ngoc dong, ngo dang
dang khoa » dung khoa, hang khoa, dang khoi
sach hoc » cach hoc, sach hoi, mach hoc
mot ngoc » mot goc, mot ngoai, mot nguoi
khoa hoc » hoa hoc
hoi chau » hoi chu, hoi cham, hai chau
phan van » pham van, thanh van, tran van
tu sach » thu sach, su sach, te sach
cuu mot » cua mot, cuu mo, huu mot
hoc xa » hoc ma
luan » quan, lan

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 cuu mot ngoc dang khoa hoc xa hoi chau ((phan van) or (luan van))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach hoc tap, nghien cuu mot ngoc dang khoa hoc xa hoi chau ((phan van) OR (luan van)).
• Adding a wildcard symbol may retrieve word variants: tu sach hoc tap, nghien cuu mot ngoc dang khoa hoc xa hoi chau ((phan van) or (luan van))*.