Perhaps you should try some spelling variations:
pham quoc » phan quoc, phim quoc, phap quoc
thanh dan » thanh san, thanh van, thanh dat
mai khoa » tai khoa, may khoa, dai khoa
su triet » su viet, su tien, ve triet
tu sach » thu sach, su sach, te sach
mai doi » moi doi, mai hoi, mai khoi
hieu vu » hieu va, hieu ve, hieu su
vu pham » su pham, vi pham, vu kham
y nang » ky nang, ly nang, v nang
dan su » dang su
gia » giao

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 y nang ((mai doi) or (mai khoa)). hieu vu pham quoc gia thanh dan su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((mai doi) OR (mai khoa)). hieu vu pham quoc gia thanh dan su triet.
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((mai doi) or (mai khoa)). hieu vu pham quoc gia thanh dan su triet*.