Perhaps you should try some spelling variations:
nham thuc » nhan thuc, nam thuc, nham thu
dan khanh » dang khanh, van khanh, dat khanh
van nham » van nam, van nhan, van tham
dan hanh » dang hanh, dan thanh, ban hanh
cau tren » cu tren, dau tren, ca tren
hieu van » hieu va, thien van, lieu va
sach ky » sac ky, sach y, sach ty
co sach » bo sach, cuon sach, hoc sach
va cau » van cau, va cac, va dau
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: co sach ky nang ((x hoi) OR (xa hoi)). hieu van nham thuc ((dan hanh) or (dan khanh)) va cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: co sach ky nang ((x hoi) OR (xa hoi)). hieu van nham thuc ((dan hanh) OR (dan khanh)) va cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "co sach ky nang ((x hoi) OR (xa hoi)). hieu van nham thuc ((dan hanh) or (dan khanh)) va cau tren".
• Adding a wildcard symbol may retrieve word variants: co sach ky nang ((x hoi) OR (xa hoi)). hieu van nham thuc ((dan hanh) or (dan khanh)) va cau tren*.