Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
khoa hoc » hoa hoc
cac vuc » cac nuoc, cac vung, cac cuoc
hanh di » hanh vi, hanh de, hang di
vuc van » duc van, luc van, thuc van
hieu ve » hieu va, hieu van
cua cau » cua cac, cua chu, cua cay
ve cac » va cac, vien cac
y hang » ly hang, ty hang, yu hang
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: ((te sach) OR (toc sach)) y hang ((khoa hoc) or (co hoc)). hieu ve cac vuc van hanh di cua cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) y hang ((khoa hoc) OR (co hoc)). hieu ve cac vuc van hanh di cua cau*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) y hang ((khoa hoc) or (co hoc)). hieu ve cac vuc van hanh di cua cau*".