Perhaps you should try some spelling variations:
va triet » va thiet, va trien, ve triet
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
sach ky » sac ky, sach y, sach kem
va hanh » van hanh, va thanh, va danh
hieu va » lieu va, hieu qua
va cam » va cham, va cac, va cao
xuc va » duc va, tuc va, luc va
cua te » cua tu

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

• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((sach ky) OR (sach ty)) nang ma hoa. hieu va cam xuc va hanh vi ((cua te) OR (va triet))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((sach ky) OR (sach ty)) nang ma hoa. hieu va cam xuc va hanh vi ((cua te) or (va triet))~".
• Adding a wildcard symbol may retrieve word variants: doc ((sach ky) OR (sach ty)) nang ma hoa. hieu va cam xuc va hanh vi ((cua te) or (va triet))*.