Perhaps you should try some spelling variations:
hoach khoi » hoach hoi, hoc khoi, hoach hoa
thu sach » tu sach, thuat sach, thuoc sach
sach da » sach dao, sach dat, sach dau
da nghe » day nghe, va nghe, dang nghe
du hoc » tu hoc, duoc hoc
su hoc » tu hoc, so hoc, su hoa
d hoc » ad hoc, de hoc, y hoc
su ho » su hoa, su pho, su co

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

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