Perhaps you should try some spelling variations:
van thiet » va thiet, dan thiet, can thiet
su sach » so sach, vu sach
hieu ve » hieu van
hieu va » lieu va, hieu qua
cac bac » cac bai, cac ban, cac cach
va tinh » may tinh
tinh va » tich va, trinh van, trinh vat
y nang » ky nang, ly nang, v nang
bac va » ban va, bac ha, bao va
x hoi » xa hoi, o hoi, 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: su sach y nang ((x hoi) or (x ho)). ((hieu ve) OR (hieu va)) cac bac va tinh va van thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach y nang ((x hoi) OR (x ho)). ((hieu ve) OR (hieu va)) cac bac va tinh va van thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach y nang ((x hoi) or (x ho)). ((hieu ve) OR (hieu va)) cac bac va tinh va van thiet".
• Adding a wildcard symbol may retrieve word variants: su sach y nang ((x hoi) or (x ho)). ((hieu ve) OR (hieu va)) cac bac va tinh va van thiet*.