Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
ban hanh » ban hang
van hanh » van thanh, van anh, van ban
cau nuoc » cap nuoc, cac nuoc, dau nuoc
hieu van » hieu va, thien van, lieu va
cho hoc » co hoc, khoa hoc
van cau » van dau, van hau, van chat
ty hang » ly hang, ty xang, thi hang
ty nang » ky nang, ty xang, ly nang
cua cau » cua cac, cua chu, cua cay
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 ((ty nang) or (ty hang)) cho hoc. hieu van cau nuoc ((van hanh) OR (ban hanh)) di cua cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ty nang) OR (ty hang)) cho hoc. hieu van cau nuoc ((van hanh) OR (ban hanh)) di cua cau*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((ty nang) or (ty hang)) cho hoc. hieu van cau nuoc ((van hanh) OR (ban hanh)) di cua cau*".