Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
duc manh » suc manh, duc anh, duc minh
dang xay » dang van, van xay
duc van » duc va, duc tan, duc phan
van cam » van nam, van lam, van cau
tu sach » thu sach, su sach, te sach
sach ty » sach y, sach tu, sach thu
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
anh vi » hanh vi, anh va, anh ve
vi cua » vai cua, di 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 ty ((nang ma) or (dang xay)) hoi. hieu van cam ((duc van) or (duc manh)) anh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty ((nang ma) OR (dang xay)) hoi. hieu van cam ((duc van) OR (duc manh)) anh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ty ((nang ma) or (dang xay)) hoi. hieu van cam ((duc van) or (duc manh)) anh vi cua tre*.