Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
sach ky » sac ky, sach y, sach ty
thuc va » thuc vat, thuc dan, thuc day
danh ve » dinh ve, anh ve, dan ve
hanh ve » hanh vi, hanh va, hanh kem
cu tren » tu tren, dua tren
x hoi » o hoi, x ho, 5 hoi

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 nang ((x hoi) or (xa hoi)). hieu van nam thuc va ((danh ve) OR (hanh ve)) cu tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang ((x hoi) OR (xa hoi)). hieu van nam thuc va ((danh ve) OR (hanh ve)) cu tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky nang ((x hoi) or (xa hoi)). hieu van nam thuc va ((danh ve) OR (hanh ve)) cu tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang ((x hoi) or (xa hoi)). hieu van nam thuc va ((danh ve) OR (hanh ve)) cu tren*.