Perhaps you should try some spelling variations:
va triet » va thiet, va trien, ve triet
sang ma » tang ma, sang tao, mang may
hanh vu » hanh vi, hanh va, hanh tu
va hanh » van hanh, va thanh, va danh
cac tuc » cac toc, cac tu, cac tac
hieu va » lieu va, hieu qua
tu sach » thu sach, te sach, tu cach
nang ma » tang ma, nang cao, mang may
su sach » so sach, vu sach
tuc va » thuc va, truc va, tuc xa
vu va » vu van, tu va, su va

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 (su sach)) ky ((nang ma) OR (sang ma)) hoi. hieu va cac tuc va hanh vu va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (su sach)) ky ((nang ma) OR (sang ma)) hoi. hieu va cac tuc va hanh vu va triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (su sach)) ky ((nang ma) OR (sang ma)) hoi. hieu va cac tuc va hanh vu va triet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (su sach)) ky ((nang ma) OR (sang ma)) hoi. hieu va cac tuc va hanh vu va triet*.