Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
thuc cay » thuc day, thuc can, thuc cao
cay vanh » cay lanh, cay xanh, cac van
vanh dai » van dai, vanh tai, lanh dao
sach vu » sach tu, sach uu, sach xu
sach va » sach xa, sach dao, sach nha
sach ha » sach nha, sach han, sach xa
cao hoi » cau hoi, co hoi, cao hoc
va tham » van tham, va cham, va thanh
cua su » qua su

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 vu) or (((sach va) OR (sach ha)))) nang cao hoi. lieu va tham thuc cay vanh dai cua su~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach vu) OR (((sach va) OR (sach ha)))) nang cao hoi. lieu va tham thuc cay vanh dai cua su.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach vu) or (((sach va) OR (sach ha)))) nang cao hoi. lieu va tham thuc cay vanh dai cua su".
• Adding a wildcard symbol may retrieve word variants: su ((sach vu) or (((sach va) OR (sach ha)))) nang cao hoi. lieu va tham thuc cay vanh dai cua su*.