Perhaps you should try some spelling variations:
dang hanh » dang thanh, ban hanh, dang hung
dang van » hoang van, hang va
sach ky » sac ky, sach y, sach ty
vu sach » vu bach, su sach, vu khach
su viet » so viet
tai su » tai so, tai tu, lai su
ha am » ha nam, ha lam, va am
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ky nang x hoi. hieu ((ha am) or (hoa am)) thuoc ((dang hanh) OR (dang van)) tai su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky nang x hoi. hieu ((ha am) OR (hoa am)) thuoc ((dang hanh) OR (dang van)) tai su viet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach ky nang x hoi. hieu ((ha am) or (hoa am)) thuoc ((dang hanh) OR (dang van)) tai su viet*".