Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hoc sach » hoc sinh, hoc cac, hoc anh
tham dan » ham dan, tam dan, tham dam
thuc van » thuc vat, thuc dan, thuc va
toc hoc » toan hoc, duoc hoc
hieu ve » hieu va, hieu van
duc van » duc va, duc tan, duc manh
minh vi » minh voi, dinh vi, minh va
cua cay » cua cac
ve cac » va cac, vien cac
vi cua » vai cua, di cua

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

• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) tham dan toc hoc. hieu ve cac ((thuc van) OR (duc van)) minh vi cua cay~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (hoc sach)) tham dan toc hoc. hieu ve cac ((thuc van) or (duc van)) minh vi cua cay~".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (hoc sach)) tham dan toc hoc. hieu ve cac ((thuc van) or (duc van)) minh vi cua cay*.