Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
ky lang » ky dang, ky tang, tay lang
hieu va » lieu va, hieu qua
nam duc » nam duoc, nam thuc, nam buoc
va hang » van hang, va nang, va lang
hang di » hang doi, hang vi, hang dien
cu tren » tu tren, dua tren
di cu » di cau, di cua, di du

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ((ky lang) or (ky nang)) xa hoi. hieu va ((nam duc) OR (pham duc)) va hang di cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ky lang) OR (ky nang)) xa hoi. hieu va ((nam duc) OR (pham duc)) va hang di cu tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((ky lang) or (ky nang)) xa hoi. hieu va ((nam duc) OR (pham duc)) va hang di cu tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ((ky lang) or (ky nang)) xa hoi. hieu va ((nam duc) OR (pham duc)) va hang di cu tren*.