Perhaps you should try some spelling variations:
cham duc » pham duc, cham soc, pham duy
dau tren » dau tien, dat tren, dau tieng
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
duc van » duc va, duc tan, duc manh
anh ve » hanh ve, anh va, thanh ve

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang x ho. ((hieu ve) or (lieu va)) cham duc van ((anh ve) OR (anh viet)) dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x ho. ((hieu ve) OR (lieu va)) cham duc van ((anh ve) OR (anh viet)) dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x ho. ((hieu ve) or (lieu va)) cham duc van ((anh ve) OR (anh viet)) dau tren".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x ho. ((hieu ve) or (lieu va)) cham duc van ((anh ve) OR (anh viet)) dau tren*.