Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, nam thuc, cam thu
su triet » su viet, su tien, ve triet
co sach » bo sach, cuon sach, hoc sach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
nang xa » nang x, lang xa, nang ma
hieu ve » hieu va
thuc va » thuc vat, thuc dan, thuc day
va lang » va nang, hoa lang
lang di » lang dai, hang di, lang du
di su » doi su, ki su, da su

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

• Performing a fuzzy search may retrieve terms with similar spellings: co sach ty nang xa hoi. ((((hieu ve) OR (hieu van))) or (hieu qua)) cam thuc va lang di su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach ty nang xa hoi. ((((hieu ve) OR (hieu van))) OR (hieu qua)) cam thuc va lang di su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "co sach ty nang xa hoi. ((((hieu ve) OR (hieu van))) or (hieu qua)) cam thuc va lang di su triet".
• Adding a wildcard symbol may retrieve word variants: co sach ty nang xa hoi. ((((hieu ve) OR (hieu van))) or (hieu qua)) cam thuc va lang di su triet*.