Perhaps you should try some spelling variations:
hoc quoc » hoc nuoc, hoc duoc, hoc thuoc
su triet » su viet, su tien, ve triet
sach tu » sach thu, sach ty, sach uu
va danh » va dinh, va dan, dia danh
va hanh » van hanh, va thanh, ban hanh
hieu va » lieu va, hieu qua
xang xa » lang xa, mang xa, ang xa
cach tu » cach thuc
va hoc » van hoc
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: vu ((sach tu) OR (cach tu)) xang xa hoi. hieu va hoc quoc ((va hanh) or (va danh)) di su triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu ((sach tu) OR (cach tu)) xang xa hoi. hieu va hoc quoc ((va hanh) OR (va danh)) di su triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu ((sach tu) OR (cach tu)) xang xa hoi. hieu va hoc quoc ((va hanh) or (va danh)) di su triet".
• Adding a wildcard symbol may retrieve word variants: vu ((sach tu) OR (cach tu)) xang xa hoi. hieu va hoc quoc ((va hanh) or (va danh)) di su triet*.