Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
thu sach » tu sach, thuat sach, thuoc sach
dang xay » dang van, van xay
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
anh vai » anh va, anh van, anh tai
ky dang » ky nang, ky danh
xay hoi » xa hoi, tay hoi, cay phoi
cac toc » cac toi, cac thoi
sach ky » sac ky, sach y, sach ty
anh bai » sach bai, danh bat, hinh bai
thiet » thieu

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 dang xay hoi. hieu vien ((cac toc) or (cac nuoc)) van ((anh vai) OR (anh bai)) va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky dang xay hoi. hieu vien ((cac toc) OR (cac nuoc)) van ((anh vai) OR (anh bai)) va thiet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky dang xay hoi. hieu vien ((cac toc) or (cac nuoc)) van ((anh vai) OR (anh bai)) va thiet".
• Adding a wildcard symbol may retrieve word variants: thu sach ky dang xay hoi. hieu vien ((cac toc) or (cac nuoc)) van ((anh vai) OR (anh bai)) va thiet*.