Perhaps you should try some spelling variations:
thieu nien » thien nhien
van hanh » van thanh, ban hanh, van anh
nien cac » vien cac, dien cac, bien cac
cac hoc » cach hoc, cac hop, bac hoc
hoc van » hoc dan, hoc va, hoc vat
ty nang » ky nang, ty hang, ly nang
su sach » so sach, vu sach
vi su » va su, ve su, oi su
ki su » ky su

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ((ty nang) OR (ty xang)) xa hoi. thieu nien cac hoc van hanh ((vi su) or (ki su)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ty nang) OR (ty xang)) xa hoi. thieu nien cac hoc van hanh ((vi su) OR (ki su)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ty nang) OR (ty xang)) xa hoi. thieu nien cac hoc van hanh ((vi su) or (ki su)) triet".
• Adding a wildcard symbol may retrieve word variants: su sach ((ty nang) OR (ty xang)) xa hoi. thieu nien cac hoc van hanh ((vi su) or (ki su)) triet*.