Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
cau thuc » cau truc, cuu thuc, can thuc
va hanh » van hanh, va thanh, ban hanh
tai cua » thai cua, tai cuc, dai cua
va danh » va dinh, va dan, dia danh
sach ky » sac ky, sach y, sach ty
van cau » van dau, van hau, van chat
dang xa » dang xay, lang xa, dang ha
ky dang » ky nang, ky danh

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