Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
doan dau » doan dieu, phan dau, doan va
dan dau » danh dau, van dau, dan dat
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
va kham » va cham, va tham, vu kham
nang ma » tang ma, sang ma, nang cao
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ky nang ma hoi. hieu ((va kham) or (va khao)) thuc vat ((dan dau) OR (doan dau)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang ma hoi. hieu ((va kham) OR (va khao)) thuc vat ((dan dau) OR (doan dau)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang ma hoi. hieu ((va kham) or (va khao)) thuc vat ((dan dau) OR (doan dau)) cua tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang ma hoi. hieu ((va kham) or (va khao)) thuc vat ((dan dau) OR (doan dau)) cua tre*.