Perhaps you should try some spelling variations:
sach kha » sach nha, sach ha, sach tham
kha nang » phap nang, ky nang, ki nang
cam thuc » cam thu, can thuc, cay thuc
nam thuc » nam thuoc, nam thu, nam tu
su triet » su viet, su tien, ve triet
su sach » so sach, vu sach
nang xa » nang x, lang xa, nang ma
hieu ve » hieu va, hieu van
va hanh » van hanh, va thanh, va danh
vi su » va su, ve su, ki su

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 kha nang xa hoi. hieu ve ((cam thuc) or (((nam thuc) OR (am thuc)))) va hanh vi su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach kha nang xa hoi. hieu ve ((cam thuc) OR (((nam thuc) OR (am thuc)))) va hanh vi su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach kha nang xa hoi. hieu ve ((cam thuc) or (((nam thuc) OR (am thuc)))) va hanh vi su triet".
• Adding a wildcard symbol may retrieve word variants: su sach kha nang xa hoi. hieu ve ((cam thuc) or (((nam thuc) OR (am thuc)))) va hanh vi su triet*.