Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
hieu van » hieu va, thien van, lieu va
van cac » van hac, van cau, van bac
mai hoi » mai khoi, dai hoi, lai hoi
ky dang » ky nang, ky danh
ky sang » ky nang, ky tang, duy sang
cuu tre » cua tre, cau tren, cau treo
ma hoi » xa hoi, ma hoa, me hoi
va dan » ca dan, va dao, va dau
dan di » danh di, dan da, dan de
di cuu » di cau, di cua, dinh cuu

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