Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thuc dan » thuc hanh, hoc dan, thuc vat
cac treo » cac tro, cau treo, cac trieu
dang xay » dang van, van xay
xay hoi » xa hoi, tay hoi, cay phoi
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
ky dang » ky nang, ky danh
dan vai » dan tai, dan vat, den vai
thuc va » thuc vat, thuc day
va nam » van nam, ha nam, va nay
dan va » doan va, dan ca, ban va

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 dang xay hoi. hieu va nam ((thuc va) or (thuc dan)) ((dan vai) OR (dan va)) cac treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky dang xay hoi. hieu va nam ((thuc va) OR (thuc dan)) ((dan vai) OR (dan va)) cac treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky dang xay hoi. hieu va nam ((thuc va) or (thuc dan)) ((dan vai) OR (dan va)) cac treo".
• Adding a wildcard symbol may retrieve word variants: toc sach ky dang xay hoi. hieu va nam ((thuc va) or (thuc dan)) ((dan vai) OR (dan va)) cac treo*.