Perhaps you should try some spelling variations:
cham luc » cham soc, nhan luc, cham cuu
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
tinh va » tich va, trinh van, trinh vat
va tinh » may tinh
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va
sang ma » tang ma, sang tao, mang may
nang ma » tang ma, nang cao, mang may
luc va » duc va, tuc va, loc va
va cua » va chua, via cua, ca cua

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 y ((nang ma) or (sang ma)) hoi. ((hieu ve) OR (hieu van)) cham luc va tinh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y ((nang ma) OR (sang ma)) hoi. ((hieu ve) OR (hieu van)) cham luc va tinh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y ((nang ma) or (sang ma)) hoi. ((hieu ve) OR (hieu van)) cham luc va tinh va cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y ((nang ma) or (sang ma)) hoi. ((hieu ve) OR (hieu van)) cham luc va tinh va cua tre*.