Perhaps you should try some spelling variations:
xanh hanh » danh thanh, ban hanh, van hanh
tham thuc » nham thuc, pham thuc, tam thuc
cham thuc » nham thuc, pham thuc, pham thuoc
su sach » so sach
hanh di » hanh vi, hanh de, hang di
vu sach » vu bach, vu khach
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
y nang » ky nang, ly nang, v nang
di cua » dai cua, doi cua, de cua
o hoi » co hoi, o hoc, o hai

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 (vu sach)) y nang o hoi. hieu va ((cham thuc) OR (tham thuc)) xanh hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (vu sach)) y nang o hoi. hieu va ((cham thuc) OR (tham thuc)) xanh hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (vu sach)) y nang o hoi. hieu va ((cham thuc) OR (tham thuc)) xanh hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (vu sach)) y nang o hoi. hieu va ((cham thuc) OR (tham thuc)) xanh hanh di cua tre*.