Perhaps you should try some spelling variations:
cau thuc » cau truc, cuu thuc, can thuc
hieu van » hieu va, thien van, lieu va
thuc va » thuc vat, thuc dan, thuc day
tu sach » thu sach, su sach, tu cach
van cau » van dau, van hau, van chat
te sach » toc sach
y nang » ky nang, ly nang, v nang
va dan » ca dan, va dao, va dau
do cua » doi cua, co cua, dong cua
de cua » le cua, te cua, dieu cua
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) OR (te sach)) y nang x hoi. hieu van cau thuc va dan ((do cua) or (de cua)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (te sach)) y nang x hoi. hieu van cau thuc va dan ((do cua) OR (de cua)) viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) OR (te sach)) y nang x hoi. hieu van cau thuc va dan ((do cua) or (de cua)) viet".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) OR (te sach)) y nang x hoi. hieu van cau thuc va dan ((do cua) or (de cua)) viet*.