Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thuc day » thuc vat
thuc dan » thuc hanh, hoc dan, thuc vat
nang xa » nang x, lang xa, nang ma
hieu ve » hieu va, hieu van
dau cua » day cua, cau cua, dan cua
y nang » ky nang, ly nang, v nang
ve cac » va cac, vien cac

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 y nang xa hoi. hieu ve cac ((thuc day) or (thuc dan)) hang ((dau cua) OR (dai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach y nang xa hoi. hieu ve cac ((thuc day) OR (thuc dan)) hang ((dau cua) OR (dai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y nang xa hoi. hieu ve cac ((thuc day) or (thuc dan)) hang ((dau cua) OR (dai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: toc sach y nang xa hoi. hieu ve cac ((thuc day) or (thuc dan)) hang ((dau cua) OR (dai cua)) tre*.