Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hanh tai » thanh tai, hang tai, han tai
hieu va » lieu va, hieu qua
tai cua » thai cua, tai cuc, tri cua
va hanh » van hanh, va thanh, va danh
cam tuc » cam xuc, cam tu, nam thuc
ky lang » ky dang, ky tang, tay lang
cua tre » cua te, cuu tre, cua triet
va cam » va cham, va cac, va cao
tuc va » thuc va, truc va, tuc xa

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((te sach) OR (toc sach)) ((ky lang) or (ky nang)) xa hoi. hieu va cam tuc va hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ((ky lang) OR (ky nang)) xa hoi. hieu va cam tuc va hanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ((ky lang) or (ky nang)) xa hoi. hieu va cam tuc va hanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ((ky lang) or (ky nang)) xa hoi. hieu va cam tuc va hanh tai cua tre*.