Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
nam thuc » nam thuoc, nam thu, nam tu
cau tren » cu tren, dau tren, ca tren
ky lang » ky dang, ky tang, tay lang
van hoi » van hoa, van hoc, van hoe
hieu va » lieu va, hieu qua
dao vai » dao van, dao va, dao bai
vai cau » va cau, van cau, vai cac
va dao » ca dao

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ((ky lang) or (ky nang)) van hoi. hieu va ((nam thuc) or (am thuc)) va dao vai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ((ky lang) OR (ky nang)) van hoi. hieu va ((nam thuc) OR (am thuc)) va dao vai cau tren.
• Adding a wildcard symbol may retrieve word variants: hoc sach ((ky lang) or (ky nang)) van hoi. hieu va ((nam thuc) or (am thuc)) va dao vai cau tren*.