Perhaps you should try some spelling variations:
thien nang » thien bang, thien dang, trien nang
dau tren » dau tien, dat tren, dau tieng
cham duc » pham duc, cham soc, phan duc
doan van » doan va, hoang van, luan van
pham duy » pham duc
van dau » van dao, phan dau
va doan » va doanh, van doan, va dan
tu sach » thu sach, su sach, tu cach
hieu ve » hieu va, hieu van
nang xa » nang x, lang xa, nang ma
te sach » toc sach

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) OR (te sach)) thien nang xa hoi. hieu ve ((cham duc) or (pham duy)) va doan van dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (te sach)) thien nang xa hoi. hieu ve ((cham duc) OR (pham duy)) va doan van dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (te sach)) thien nang xa hoi. hieu ve ((cham duc) or (pham duy)) va doan van dau tren".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (te sach)) thien nang xa hoi. hieu ve ((cham duc) or (pham duy)) va doan van dau tren*.