Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thanh di » thanh doi, thanh de, thanh do
thuc dan » thuc hanh, hoc dan
hieu va » lieu va, hieu qua
va than » va thanh, van than, va phan
nang co » nang cao, nang doc, nang noi
so sach » so sanh, bo sach, co sach
co hoi » co hoc, co loi
ca tra » cau tra, ca tru, va tra
di ca » di cau, di cua, doi ca

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 (so sach)) ky nang co hoi. hieu va than ((thuc dan) OR (thuc vat)) thanh di ca tra~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (so sach)) ky nang co hoi. hieu va than ((thuc dan) OR (thuc vat)) thanh di ca tra.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (so sach)) ky nang co hoi. hieu va than ((thuc dan) OR (thuc vat)) thanh di ca tra".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (so sach)) ky nang co hoi. hieu va than ((thuc dan) OR (thuc vat)) thanh di ca tra*.