Perhaps you should try some spelling variations:
cua triet » cua viet, su triet, va triet
nang cai » nang cao, nang tai, nang can
nang cap » nang cao, nang cham, nang phap
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, dua tren
ve cac » va cac, vien cac

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 ky ((nang cai) OR (nang cap)) hoi. hieu ve cac nuoc va hanh vi ((cua tre) or (cua triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang cai) OR (nang cap)) hoi. hieu ve cac nuoc va hanh vi ((cua tre) OR (cua triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang cai) OR (nang cap)) hoi. hieu ve cac nuoc va hanh vi ((cua tre) or (cua triet))".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang cai) OR (nang cap)) hoi. hieu ve cac nuoc va hanh vi ((cua tre) or (cua triet))*.