Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thai cua » than cua, tai cuc, tri cua
ky dang » ky nang, ky danh
dang xa » dang xay, lang xa, dang ha
hieu va » lieu va, hieu qua
va danh » va dinh, va dan, va hanh
co duc » co duoc, cao duc, do duc
va co » vo co

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 dang xa hoi. hieu va co duc va danh ((dai cua) or (thai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (toc sach)) ky dang xa hoi. hieu va co duc va danh ((dai cua) OR (thai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) OR (toc sach)) ky dang xa hoi. hieu va co duc va danh ((dai cua) or (thai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: ((te sach) OR (toc sach)) ky dang xa hoi. hieu va co duc va danh ((dai cua) or (thai cua)) tre*.