Perhaps you should try some spelling variations:
sach kha » sach ha, sach tham, bach khoa
cam thuc » am thuc, cam thu, can thuc
nam thuc » nam thuoc, am thuc, nam thu
van hanh » van thanh, ban hanh, van anh
su triet » su viet, su tien, ve triet
nang xa » nang x, lang xa, nang ma
hieu ve » hieu va, hieu van
hanh va » hang va, hanh vi

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