Perhaps you should try some spelling variations:
ngang duoc » nganh duoc, nhan duoc
cau tren » cu tren, dau tren, ca tren
duoc hoi » quoc hoi, duoc hoc, duoc si
hieu van » thien van, lieu va, hieu ve
sach thu » sach thue, sach thieu, sach tham
sach tu » cach tu, sach ty, sach uu
hieu va » lieu va, hieu qua
nam luc » nang luc, nhan luc, nam thuc
va hanh » van hanh, va thanh, va danh
hanh va » hang va, hanh vi
luc va » duc va, tuc va, loc va
va cau » van cau, va cac, va dau

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 tu) or (sach thu)) ngang duoc hoi. ((hieu van) OR (hieu va)) nam luc va hanh va cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach tu) OR (sach thu)) ngang duoc hoi. ((hieu van) OR (hieu va)) nam luc va hanh va cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach tu) or (sach thu)) ngang duoc hoi. ((hieu van) OR (hieu va)) nam luc va hanh va cau tren".
• Adding a wildcard symbol may retrieve word variants: tu ((sach tu) or (sach thu)) ngang duoc hoi. ((hieu van) OR (hieu va)) nam luc va hanh va cau tren*.