Perhaps you should try some spelling variations:
doc sach » toc sach, nuoc sach, dac sac
hoc sach » hoc sinh, hoc cac, hoc anh
van hang » van khang, van hoang, van thang
hang tai » hang va, dung tai
cau tren » cu tren, dau tren, ca tren
hieu va » lieu va, hieu qua
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
tai cau » tai cac, tai cao
x hoi » xa hoi, o hoi, x ho

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((doc sach) or (hoc sach)) ky nang x hoi. hieu va cac duc van hang tai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((doc sach) OR (hoc sach)) ky nang x hoi. hieu va cac duc van hang tai cau tren.
• Adding a wildcard symbol may retrieve word variants: ((doc sach) or (hoc sach)) ky nang x hoi. hieu va cac duc van hang tai cau tren*.