Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
thuc dan » thuc hanh, hoc dan, thuc vat
thuc van » thuc vat, thuc va, thuc hanh
co sach » bo sach, cuon sach, hoc sach
hanh di » hanh vi, hanh de, hang di
ve pham » vi pham, v pham, ve phan
hieu ve » hieu va, hieu van
nang xa » nang x, lang xa, nang ma
cua tre » cua te, cuu tre, cua triet
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: ((co sach) or (doc sach)) ky nang xa hoi. hieu ve pham ((thuc van) OR (thuc dan)) hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((co sach) OR (doc sach)) ky nang xa hoi. hieu ve pham ((thuc van) OR (thuc dan)) hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((co sach) or (doc sach)) ky nang xa hoi. hieu ve pham ((thuc van) OR (thuc dan)) hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: ((co sach) or (doc sach)) ky nang xa hoi. hieu ve pham ((thuc van) OR (thuc dan)) hanh di cua tre*.