Perhaps you should try some spelling variations:
cham thuc » nham thuc, pham thuc, tham thuc
thien van » thi van
vat hanh » vat thanh, van hanh, va hanh
cau tren » cu tren, dau tren, ca tren
co sach » bo sach, cuon sach, hoc sach
hieu ve » hieu va, hieu van
hanh va » hang va, hanh vi
y nang » ky nang, ly nang, v nang
va cau » van cau, va cac, va dau
x hoi » xa hoi, o hoi, 5 hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: co sach y nang ((x hoi) or (x ho)). ((hieu ve) or (thien van)) cham thuc vat hanh va cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach y nang ((x hoi) OR (x ho)). ((hieu ve) OR (thien van)) cham thuc vat hanh va cau tren.
• Adding a wildcard symbol may retrieve word variants: co sach y nang ((x hoi) or (x ho)). ((hieu ve) or (thien van)) cham thuc vat hanh va cau tren*.