Perhaps you should try some spelling variations:
cau thuc » cau truc, cuu thuc, can thuc
vat hanh » vat thanh, van hanh, va hanh
vu sach » vu bach, su sach, vu khach
ty lang » tay lang, ty xang, tu lang
ty hang » ly hang, ty xang, thi hang
hieu ke » hieu kem, chieu ke, hieu ky
ke cau » ket cau
vi cua » vai cua
di cua » dai cua, doi cua, de cua

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 ((ty lang) or (ty hang)) xa hoi. hieu ke cau thuc vat hanh ((vi cua) OR (di cua)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ((ty lang) OR (ty hang)) xa hoi. hieu ke cau thuc vat hanh ((vi cua) OR (di cua)) triet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach ((ty lang) or (ty hang)) xa hoi. hieu ke cau thuc vat hanh ((vi cua) OR (di cua)) triet".
• Adding a wildcard symbol may retrieve word variants: vu sach ((ty lang) or (ty hang)) xa hoi. hieu ke cau thuc vat hanh ((vi cua) OR (di cua)) triet*.