Perhaps you should try some spelling variations:
sach day » sach dao, sach dat, sach dau
day nghe » dang nghe, van nghe, nam nghe
hoach ha » hoach va, hoach hoi, hoach su
tu sach » thu sach, su sach, te sach
nghe de » nghe det, nghe di, nghe te
de hoc » te hoc, du hoc, dien hoc
su hoa » su hoan, su hoat, su khoa
tu hoc » te 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 day nghe de hoc ) or ( thu ((hoach ha) OR (hoach xay)) nghiem ((su hoa) or (tu hoc)) ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu sach day nghe de hoc ) OR ( thu ((hoach ha) OR (hoach xay)) nghiem ((su hoa) OR (tu hoc)) )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu sach day nghe de hoc ) or ( thu ((hoach ha) OR (hoach xay)) nghiem ((su hoa) or (tu hoc)) ))".
• Adding a wildcard symbol may retrieve word variants: (( tu sach day nghe de hoc ) or ( thu ((hoach ha) OR (hoach xay)) nghiem ((su hoa) or (tu hoc)) ))*.