Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cam thuc » am thuc, nam thuc, cam thu
thuc van » thuc vat, thuc dan, thuc va
van hanh » van thanh, ban hanh, van anh
hieu ve » hieu va, hieu van
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
y lang » o lang, tay lang, yen lang
_ lang » o lang, _ land
ve cam » ve cham, ve cac, va cam
di cua » dai cua, doi cua, de cua

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 ((y lang) or (_ lang)) xa hoi. hieu ve cam thuc van hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((y lang) OR (_ lang)) xa hoi. hieu ve cam thuc van hanh di cua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ((y lang) or (_ lang)) xa hoi. hieu ve cam thuc van hanh di cua tre*.