Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
ban hanh » ban hang
va thanh » gia thanh, ban thanh, va tinh
sach ky » sac ky, sach y, sach ty
nang xa » nang x, lang xa, nang ma
hieu va » lieu va, hieu qua
va pham » van pham, va phat, va phap
va hanh » van hanh, va danh, dao hanh
cua tre » cua te, cuu tre, cua triet

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 ky nang xa hoi. hieu va pham duc ((((va hanh) OR (ban hanh))) or (va thanh)) dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang xa hoi. hieu va pham duc ((((va hanh) OR (ban hanh))) OR (va thanh)) dai cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang xa hoi. hieu va pham duc ((((va hanh) OR (ban hanh))) or (va thanh)) dai cua tre*".