Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thuc dan » thuc hanh, hoc dan, thuc vat
sach ky » sac ky, sach y, sach ty
xay hoi » xa hoi, tay hoi, cay phoi
thuc va » thuc vat, thuc day
dau vai » dau va, dau hai, dau tai
vai cuu » vai cua
cuu tre » cua tre, cau tren, cau treo
ky van » ly van, ty van, ky va
va nam » ha nam, va nay

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 van xay hoi. hieu ((va nam) or (van nam)) ((thuc va) OR (thuc dan)) dau vai cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky van xay hoi. hieu ((va nam) OR (van nam)) ((thuc va) OR (thuc dan)) dau vai cuu tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky van xay hoi. hieu ((va nam) or (van nam)) ((thuc va) OR (thuc dan)) dau vai cuu tre*".