Perhaps you should try some spelling variations:
sach duoc » sach nuoc, sach dao, sach dung
cham thuc » nham thuc, pham thuc, tham thuc
sach vuc » sach nuoc, sach truc, sach bac
van hanh » van thanh, ban hanh, van anh
vat hanh » vat thanh, va hanh, nhat hanh
hieu ve » hieu va, hieu van
ve cham » va cham, ve chat, vu cham
cuu tre » cua tre, cau tren, cau treo
nang o » nang co, nang ho, nang ro
di cuu » di cau, di cua, dinh cuu
o hai » co hai, so hai, o lai

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 vuc) or (sach duoc)) nang o hai. hieu ve cham thuc ((vat hanh) OR (van hanh)) di cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach vuc) OR (sach duoc)) nang o hai. hieu ve cham thuc ((vat hanh) OR (van hanh)) di cuu tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach vuc) or (sach duoc)) nang o hai. hieu ve cham thuc ((vat hanh) OR (van hanh)) di cuu tre*".