Perhaps you should try some spelling variations:
su triet » su viet, su tien, ve triet
hieu van » hieu va, thien van, lieu va
sach thu » sach thue, sach thieu, sach tham
tinh vi » trinh vi, tinh voi, tinh va
thuc va » thuc vat, thuc dan, thuc day
truc va » thuc vat, trung va
sach tu » cach tu, sach ty, sach uu
van cac » van hac, van cau, van bac
xang x » nang x
x hoi » xa hoi, o hoi, x ho
vi su » va su, ve su, ki su

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach thu) or (sach tu)) xang x hoi. hieu van cac ((truc va) OR (thuc va)) tinh vi su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach thu) OR (sach tu)) xang x hoi. hieu van cac ((truc va) OR (thuc va)) tinh vi su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach thu) or (sach tu)) xang x hoi. hieu van cac ((truc va) OR (thuc va)) tinh vi su triet".
• Adding a wildcard symbol may retrieve word variants: su ((sach thu) or (sach tu)) xang x hoi. hieu van cac ((truc va) OR (thuc va)) tinh vi su triet*.