Perhaps you should try some spelling variations:
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
nang ma » sang ma, nang cao, mang may
tang ma » mang may, tang van
hieu le » hieu ve, hieu he, hieu ly
va hanh » van hanh, va thanh, va danh
cuu tre » cau tren, cau treo
cua tre » cua te, cua triet, dua tren
le dat » le dan, de dat, le dac
nuoc » quoc, duoc, ngoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky ((nang ma) OR (tang ma)) hoi. hieu le dat nuoc va hanh vi ((cuu tre) or (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky ((nang ma) OR (tang ma)) hoi. hieu le dat nuoc va hanh vi ((cuu tre) OR (cua tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky ((nang ma) OR (tang ma)) hoi. hieu le dat nuoc va hanh vi ((cuu tre) or (cua tre))".
• Adding a wildcard symbol may retrieve word variants: so sach ky ((nang ma) OR (tang ma)) hoi. hieu le dat nuoc va hanh vi ((cuu tre) or (cua tre))*.