Perhaps you should try some spelling variations:
quoc quan » qua quan, luc quan, hoc quan
quoc ban » quoc bao, quoc lan, quoc binh
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
vai cua » dai cua, hai cua, lai cua
y nang » ky nang, ly nang, v nang
ve cam » ve cham, ve cac, va cam
vi cua » di cua
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: tu sach y nang x hoi. hieu ve cam ((quoc ban) OR (quoc quan)) anh ((vi cua) or (vai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang x hoi. hieu ve cam ((quoc ban) OR (quoc quan)) anh ((vi cua) OR (vai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang x hoi. hieu ve cam ((quoc ban) OR (quoc quan)) anh ((vi cua) or (vai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang x hoi. hieu ve cam ((quoc ban) OR (quoc quan)) anh ((vi cua) or (vai cua)) tre*.