Perhaps you should try some spelling variations:
thien van » thi van
kho tang » cao tang
nam thuc » nam thuoc, am thuc, nam thu
tu sach » thu sach, su sach, te sach
hang di » hang doi, hang vi, hang dien
va hang » van hang, va nang, va lang
nam luc » nang luc, nhan luc, nam duoc
ky tang » ky nang, ky dang, ky trong
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: tu sach ((ky tang) OR (kho tang)) xa hoi. thien van ((nam luc) or (nam thuc)) va hang di cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky tang) OR (kho tang)) xa hoi. thien van ((nam luc) OR (nam thuc)) va hang di cu tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((ky tang) OR (kho tang)) xa hoi. thien van ((nam luc) or (nam thuc)) va hang di cu tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky tang) OR (kho tang)) xa hoi. thien van ((nam luc) or (nam thuc)) va hang di cu tren*.