Perhaps you should try some spelling variations:
cac trung » cac truong, dac trung, bac trung
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, van anh, van ban
ban hanh » ban hang
cao hoi » cau hoi, co hoi, cao hoc
cho hoc » co hoc, khoa hoc
hieu ve » hieu va, hieu van
luu tre » luu tru, cuu tre, luy tre
y nang » ky nang, ly nang, v nang
ve cac » va cac, vien cac
vi luu » vi lua

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 nang ((cao hoi) or (cho hoc)). hieu ve cac trung ((van hanh) OR (ban hanh)) vi luu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y nang ((cao hoi) OR (cho hoc)). hieu ve cac trung ((van hanh) OR (ban hanh)) vi luu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y nang ((cao hoi) or (cho hoc)). hieu ve cac trung ((van hanh) OR (ban hanh)) vi luu tre".
• Adding a wildcard symbol may retrieve word variants: toc sach y nang ((cao hoi) or (cho hoc)). hieu ve cac trung ((van hanh) OR (ban hanh)) vi luu tre*.