Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
nay thuc » nam thuc, cay thuc, day thuc
cau tren » cu tren, dau tren, ca tren
hoc sach » hoc sinh, hoc cac, hoc anh
lang van » dang van, tang van, hoang van
thuc dan » thuc hanh, hoc dan, thuc vat
dan tai » van tai, dan thi, han tai
dan dan » dang dan, ban dan, dao dan
hieu va » lieu va, hieu qua
van hoi » van hoa, van hoc, van hoe
ky lang » ky nang, ky dang, ky tang
va nay » va ngay, va cay
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((toc sach) or (hoc sach)) ky lang van hoi. hieu va nay thuc dan dan tai ((cau tren) or (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) ky lang van hoi. hieu va nay thuc dan dan tai ((cau tren) OR (cua te)).
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc sach)) ky lang van hoi. hieu va nay thuc dan dan tai ((cau tren) or (cua te))*.