Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
nam thuc » nam thuoc, am thuc, nam thu
may thoi » gay thoi, may thi, tay thoi
cay mang » cach mang, cay mac, cay cong
may hoi » tay hoi, mai hoi, may hmi
hieu he » hieu ve, hiem he, hieu le
thuc va » thuc vat, thuc dan, thuc day
va danh » va dinh, va dan, va hanh
danh vi » hanh vi, dinh vi, danh di
he nam » ha nam, nghe nam
vi hoa » voi hoa, vi hoc, va hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sach ((y mang) OR (cay mang)) ((may hoi) or (may thoi)). hieu he nam thuc va danh vi hoa viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sach ((y mang) OR (cay mang)) ((may hoi) OR (may thoi)). hieu he nam thuc va danh vi hoa viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sach ((y mang) OR (cay mang)) ((may hoi) or (may thoi)). hieu he nam thuc va danh vi hoa viet".
• Adding a wildcard symbol may retrieve word variants: hoc sach ((y mang) OR (cay mang)) ((may hoi) or (may thoi)). hieu he nam thuc va danh vi hoa viet*.