Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
hoach va » hoach xay, hanh va, hoa va
doanh va » doan va, doanh tai, doanh cua
tu sach » su sach, te sach, tu cach
da nghe » day nghe, va nghe, dang nghe
nghe d » nghe di, nghe _, nghe 新
d hoc » du hoc, ad hoc, de hoc

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( ((tu sach) OR (thu sach)) da nghe d hoc ) or ( thu ((hoach va) or (doanh va)) nghiem ngu hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( ((tu sach) OR (thu sach)) da nghe d hoc ) OR ( thu ((hoach va) OR (doanh va)) nghiem ngu hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( ((tu sach) OR (thu sach)) da nghe d hoc ) or ( thu ((hoach va) or (doanh va)) nghiem ngu hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( ((tu sach) OR (thu sach)) da nghe d hoc ) or ( thu ((hoach va) or (doanh va)) nghiem ngu hoc ))*.