Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
nam thuc » nam thuoc, am thuc, nam thu
cam thuc » am thuc, cam thu, can thuc
su sach » so sach, vu sach
hanh di » hanh vi, hanh de, hang di
cua tre » cua te, cuu tre, cua triet
nang xa » lang xa, nang ma, mang xa
hieu ve » hieu va, hieu van
sach v » sach va, sach y, sach 2
di cua » dai cua, doi cua, de cua

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 v ((nang xa) or (nang x)) hoi. hieu ve ((cam thuc) OR (nam thuc)) van hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach v ((nang xa) OR (nang x)) hoi. hieu ve ((cam thuc) OR (nam thuc)) van hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach v ((nang xa) or (nang x)) hoi. hieu ve ((cam thuc) OR (nam thuc)) van hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach v ((nang xa) or (nang x)) hoi. hieu ve ((cam thuc) OR (nam thuc)) van hanh di cua tre*.