Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
doan vai » doan van, doan hai, doan vi
cau tren » cu tren, ca tren, cau treo
dau tren » dau tien, dat tren, dau tieng
sach ty » sach y, sach tu, sach thu
ty lang » tay lang, ty xang, ty hang
lang xa » lang ha, dang xay, lang van
hieu ha » hieu hoa, hieu va, hieu ca
thuc va » thuc vat, thuc dan, thuc day

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: toc sach ty lang xa hoi. hieu ha nam thuc va ((doan vai) OR (doan va)) ((cau tren) OR (dau tren))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ty lang xa hoi. hieu ha nam thuc va ((doan vai) or (doan va)) ((cau tren) OR (dau tren))~".
• Adding a wildcard symbol may retrieve word variants: toc sach ty lang xa hoi. hieu ha nam thuc va ((doan vai) or (doan va)) ((cau tren) OR (dau tren))*.