Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
hieu va » lieu va, hieu qua
tai cua » thai cua, tai cuc, tri cua
kham ly » khao ly, khanh ly
cua tre » cua te, cuu tre, cua triet
hieu vu » hieu ve, hieu su, dieu vu
ty hang » ly hang, ty xang, thi hang
ty nang » ky nang, ty xang, ly nang
ly van » le van, ly va, ly von

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ((ty nang) or (ty hang)) ma hoa. ((hieu vu) OR (hieu va)) kham ly van hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ty nang) OR (ty hang)) ma hoa. ((hieu vu) OR (hieu va)) kham ly van hanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((ty nang) or (ty hang)) ma hoa. ((hieu vu) OR (hieu va)) kham ly van hanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: thu sach ((ty nang) or (ty hang)) ma hoa. ((hieu vu) OR (hieu va)) kham ly van hanh tai cua tre*.