Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
tinh di » tinh doi, trinh di, tinh da
duy may » duy mai, dung may, duy thay
ve phan » va phan, ke phan, ve phat
ve pham » vi pham, v pham, ve phat
sach tu » sach thu, cach tu, sach uu
nang xa » nang x, lang xa, nang ma
sach ty » sach y, sach thu, xach tay
di su » doi su, ki su, da su

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 tu) or (sach ty)) nang xa hoi. hieu ((ve pham) OR (ve phan)) duy may tinh di su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach tu) OR (sach ty)) nang xa hoi. hieu ((ve pham) OR (ve phan)) duy may tinh di su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach tu) or (sach ty)) nang xa hoi. hieu ((ve pham) OR (ve phan)) duy may tinh di su triet".
• Adding a wildcard symbol may retrieve word variants: tu ((sach tu) or (sach ty)) nang xa hoi. hieu ((ve pham) OR (ve phan)) duy may tinh di su triet*.