Perhaps you should try some spelling variations:
duy sang » duy van, duy can, duy anh
so sach » so sanh, bo sach, co sach
va hanh » van hanh, va thanh, va danh
cuu tre » cua tre, cau tren, cau treo
ma hoi » mai hoi, xa hoi, ma hoa
y sang » _ sang
le dat » de dat, le dac, ve dat
le dan » ke dan
vi cuu » vi luu, vinh cuu

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