Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
day hang » dat hang, dai hang, day nang
thuc day » thuc dan, thuc vat
nam thuc » nam thuoc, am thuc, nam thu
su triet » su viet, su tien, ve triet
nang xa » nang x, lang xa, nang ma
hieu he » hieu ve, hiem he, hieu hien
hieu le » hieu ve, hieu ly, tieu le
so sach » so sanh, bo sach, co sach
hang vi » hang va, hanh vi, hang di
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: ((toc sach) or (so sach)) ky nang xa hoi. ((hieu he) OR (hieu le)) nam thuc day hang vi su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (so sach)) ky nang xa hoi. ((hieu he) OR (hieu le)) nam thuc day hang vi su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (so sach)) ky nang xa hoi. ((hieu he) OR (hieu le)) nam thuc day hang vi su triet".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (so sach)) ky nang xa hoi. ((hieu he) OR (hieu le)) nam thuc day hang vi su triet*.