Perhaps you should try some spelling variations:
dieu cua » dieu tra
so sach » so sanh, bo sach, co sach
toc gia » toc giay, tac gia, quoc gia
cam toc » cac toc, cao toc
hieu va » lieu va, hieu qua
ly nang » ky nang, ly hang, ly vang
co hoi » co hoc, co loi
y nang » ky nang, v nang, may nang
va cam » va cham, va cac, va cao
de cua » le cua, te cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ((y nang) OR (ly nang)) co hoi. hieu va cam toc gia thanh ((de cua) or (dieu cua)) te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ((y nang) OR (ly nang)) co hoi. hieu va cam toc gia thanh ((de cua) OR (dieu cua)) te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ((y nang) OR (ly nang)) co hoi. hieu va cam toc gia thanh ((de cua) or (dieu cua)) te".
• Adding a wildcard symbol may retrieve word variants: so sach ((y nang) OR (ly nang)) co hoi. hieu va cam toc gia thanh ((de cua) or (dieu cua)) te*.