Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach van » sach han, sach va, bach van
dat tren » dat trong, dua tren
qua cam » qua cham, qua cac, qua ca
va danh » va dinh, va dan, va hanh
danh di » danh du, xanh di, danh dien
cuu tre » cua tre, cau tren, cau treo
cam luc » cam xuc, cau luc
luc va » duc va, tuc va, loc va
o lai » o lao
o hai » co hai, so hai, _ hai

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 van ban ((o hai) OR (o lai)). hieu qua cam luc va danh di ((cuu tre) OR (dat tren))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach van ban ((o hai) OR (o lai)). hieu qua cam luc va danh di ((cuu tre) or (dat tren))~".
• Adding a wildcard symbol may retrieve word variants: toc sach van ban ((o hai) OR (o lai)). hieu qua cam luc va danh di ((cuu tre) or (dat tren))*.