Perhaps you should try some spelling variations:
sach thuc » cach thuc, sach thu, sach thue
cau tren » cu tren, dau tren, ca tren
vu sach » vu bach, su sach, vu khach
hieu ve » hieu va, hieu van
hanh ve » hanh vi, hanh va, hanh kem
ve cac » va cac, vien cac
x hoi » xa hoi, o hoi, 5 hoi
du va » dau va, tu va, su va

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach thuc hanh ((x hoi) OR (x ho)). hieu ve cac du va ((hanh ve) or (hang va)) cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach thuc hanh ((x hoi) OR (x ho)). hieu ve cac du va ((hanh ve) OR (hang va)) cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach thuc hanh ((x hoi) OR (x ho)). hieu ve cac du va ((hanh ve) or (hang va)) cau tren".
• Adding a wildcard symbol may retrieve word variants: vu sach thuc hanh ((x hoi) OR (x ho)). hieu ve cac du va ((hanh ve) or (hang va)) cau tren*.