Perhaps you should try some spelling variations:
va trien » va truyen, va thiet, va tuyen
va triet » va thiet, ve triet, cua triet
hieu van » hieu va, thien van, lieu va
cau thuc » cau truc, cuu thuc, can thuc
song xa » song cua
van cau » van dau, van hau, van chat
thuc va » thuc vat, thuc dan, thuc day
va danh » va dinh, va dan, va hanh
danh vu » danh tu, anh vu, danh du
co sach » bo sach, cuon sach, hoc sach
su sach » so sach, vu sach
y song » _ song, c song, k song

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) or (co sach)) y song xa hoi. hieu van cau thuc va danh vu ((va triet) OR (va trien))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (co sach)) y song xa hoi. hieu van cau thuc va danh vu ((va triet) OR (va trien)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (co sach)) y song xa hoi. hieu van cau thuc va danh vu ((va triet) OR (va trien))".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (co sach)) y song xa hoi. hieu van cau thuc va danh vu ((va triet) OR (va trien))*.