Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
dau thuc » dan thuc, dai thuc, dam thuc
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
hieu va » lieu va, hieu qua
vu dang » su dang, vu quang, cua dang
vu lang » va lang, cu lang, tu lang
va dau » va dao
vi cua » vai cua, di cua
cua te » cua tu

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