Perhaps you should try some spelling variations:
tham thuc » nham thuc, pham thuc, tam thuc
van thanh » ban thanh, van tuan
doc sach » hoc sach, toc sach, nuoc sach
van hanh » ban hanh, van anh, van ban
ve tham » va tham, ve cham, vi tham
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
y lang » _ lang, tay lang, yen lang
o lang » hoa lang, hoi lang
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ((y lang) or (o lang)) van hoa. hieu ve tham thuc ((van hanh) OR (van thanh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ((y lang) OR (o lang)) van hoa. hieu ve tham thuc ((van hanh) OR (van thanh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ((y lang) or (o lang)) van hoa. hieu ve tham thuc ((van hanh) OR (van thanh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: doc sach ((y lang) or (o lang)) van hoa. hieu ve tham thuc ((van hanh) OR (van thanh)) vi cua tre*.