Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
dang xay » dang van, van xay
hanh tai » thanh tai, hang tai, han tai
nam truc » nam truoc, nam thuc, nam trung
hieu van » hieu va, thien van, lieu va
sach ky » sac ky, sach y, sach ty
nam tuc » nam thuc, nam tu, nam thuoc
dang xa » lang xa, dang ha, dang va
va hanh » van hanh, va thanh, va danh
tai cua » thai cua, tai cuc, tri cua
cua tu » cua tuc, cua su, cua cu

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