Perhaps you should try some spelling variations:
cam thuc » am thuc, nam thuc, cam thu
vai cuu » vai cua
su sach » so sach, vu sach
hieu ve » hieu va, hieu van
ly nang » ky nang, ly hang, ly vang
cuu tre » cua tre, cau tren, cau treo
ve cam » ve cham, ve cac, va cam
va dan » ca dan, va dau, va dap
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: su sach ((ly nang) or (ty xang)) xa hoi. hieu ve cam thuc ((va dan) OR (va dao)) vai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ly nang) OR (ty xang)) xa hoi. hieu ve cam thuc ((va dan) OR (va dao)) vai cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ly nang) or (ty xang)) xa hoi. hieu ve cam thuc ((va dan) OR (va dao)) vai cuu tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((ly nang) or (ty xang)) xa hoi. hieu ve cam thuc ((va dan) OR (va dao)) vai cuu tre*.