Perhaps you should try some spelling variations:
van hoang » van hoan, quan hoang, tran hoang
cau tren » cu tren, dau tren, ca tren
cam thuc » am thuc, nam thuc, cam thu
van hang » van khang, van thang, ban hang
te sach » toc sach
hieu ve » hieu va, hieu van
nang xa » nang x, lang xa, nang ma
so sanh » do sanh
di cau » da cau, diem cau
ve cam » ve cham, ve cac, va cam

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 (so sanh)) ky nang xa hoi. hieu ve cam thuc ((van hang) OR (van hoang)) di cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (so sanh)) ky nang xa hoi. hieu ve cam thuc ((van hang) OR (van hoang)) di cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (so sanh)) ky nang xa hoi. hieu ve cam thuc ((van hang) OR (van hoang)) di cau tren".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (so sanh)) ky nang xa hoi. hieu ve cam thuc ((van hang) OR (van hoang)) di cau tren*.