Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cua viet » ca viet, hoa viet, cua vat
hieu va » lieu va, hieu qua
cac duc » cac du, cao duc, cac dac
va tinh » may tinh
tinh de » tinh da, sinh de, tinh he
y dang » ky dang, 2 dang, _ dang
co hai » co dai, co hoi, so hai
de cua » le cua, te cua, dieu cua
o hai » so hai, o lai, _ hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) or (toc sach)) y dang ((o hai) or (co hai)). hieu va cac duc va tinh de cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) y dang ((o hai) OR (co hai)). hieu va cac duc va tinh de cua viet.
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (toc sach)) y dang ((o hai) or (co hai)). hieu va cac duc va tinh de cua viet*.