Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
thuc dan » thuc hanh, hoc dan, thuc vat
cua viet » ca viet, hoa viet, cua vat
hieu vu » hieu va, hieu ve, hieu su
vu cham » va cham, vu kham, tu cham
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
ty nang » ky nang, ty xang, ty hang
dinh vi » dinh ve, dinh viet, dinh tri
thuc va » thuc vat, thuc day
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 ty nang ma hoi. hieu vu cham ((thuc va) OR (thuc dan)) ((dinh vi) or (chinh tri)) cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty nang ma hoi. hieu vu cham ((thuc va) OR (thuc dan)) ((dinh vi) OR (chinh tri)) cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ty nang ma hoi. hieu vu cham ((thuc va) OR (thuc dan)) ((dinh vi) or (chinh tri)) cua viet".
• Adding a wildcard symbol may retrieve word variants: toc sach ty nang ma hoi. hieu vu cham ((thuc va) OR (thuc dan)) ((dinh vi) or (chinh tri)) cua viet*.