Perhaps you should try some spelling variations:
hieu thien » hieu hien, chieu chien, dieu khien
thach duc » thach thuc, than duc, thinh duc
hach xuc » hanh xu, cach xu, mach xu
tinh va » tich va, trinh van, trinh vat
tu sach » thu sach, su sach, te sach
ty hang » ly hang, ty xang, thi hang
ty nang » ky nang, ty xang, ly nang
chu tre » cho tre, chu tri, cuu tre
va chu » va che, va cau, va chi
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 ((ty nang) or (ty hang)) x hoi. hieu thien ((hach xuc) OR (thach duc)) may tinh va chu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ty nang) OR (ty hang)) x hoi. hieu thien ((hach xuc) OR (thach duc)) may tinh va chu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ty nang) or (ty hang)) x hoi. hieu thien ((hach xuc) OR (thach duc)) may tinh va chu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ty nang) or (ty hang)) x hoi. hieu thien ((hach xuc) OR (thach duc)) may tinh va chu tre*.