Perhaps you should try some spelling variations:
thuoc sach » hoc sach, nuoc sach, thuat sach
tham thuc » nham thuc, pham thuc, tam thuc
van tham » van thanh, van tuan, van chat
hieu van » hieu va, thien van, lieu va
tu cach » tu cac
va hanh » van hanh, va thanh, va danh
thuc va » thuc vat, thuc dan, thuc day
mai hoi » mai khoi, dai hoi, lai hoi
ky sang » ky dang, ky tang, duy sang
cua tre » cua te, cuu tre, cua triet
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: ((tu cach) or (thuoc sach)) ((ky sang) OR (ky nang)) mai hoi. hieu van tham thuc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu cach) OR (thuoc sach)) ((ky sang) OR (ky nang)) mai hoi. hieu van tham thuc va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu cach) or (thuoc sach)) ((ky sang) OR (ky nang)) mai hoi. hieu van tham thuc va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((tu cach) or (thuoc sach)) ((ky sang) OR (ky nang)) mai hoi. hieu van tham thuc va hanh vi cua tre*.