Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
sach tay » xach tay, sach hay, sach nay
trung ha » trung hoc, trung cap
cam thuc » am thuc, nam thuc, cam thu
cau tren » cu tren, dau tren, ca tren
hieu va » lieu va, hieu qua
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
hanh va » hang va, hanh vi
va cam » va cham, va cac, va cao
va cau » van cau, va cac, va dau

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 tay ((trung ha) or (trung tam)) hoi. hieu va cam thuc va hanh va cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach tay ((trung ha) OR (trung tam)) hoi. hieu va cam thuc va hanh va cau tren.
• Adding a wildcard symbol may retrieve word variants: toc sach tay ((trung ha) or (trung tam)) hoi. hieu va cam thuc va hanh va cau tren*.