Perhaps you should try some spelling variations:
doanh tri » doanh tai, doanh tren, dinh tri
va doanh » van doanh, vay doanh, va danh
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
lang xa » lang ha, dang xay, lang van
cam duc » cao duc, pham duc, nam duoc
cua tre » cua te, cuu tre, cua triet

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 ty ((mang may) or (lang xa)) hoi. hieu qua ((cam duc) OR (cam xuc)) va doanh tri cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((mang may) OR (lang xa)) hoi. hieu qua ((cam duc) OR (cam xuc)) va doanh tri cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ty ((mang may) or (lang xa)) hoi. hieu qua ((cam duc) OR (cam xuc)) va doanh tri cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((mang may) or (lang xa)) hoi. hieu qua ((cam duc) OR (cam xuc)) va doanh tri cua tre*.