Perhaps you should try some spelling variations:
nang dai » nang dau, nang tai, lang dai
hanh hai » thanh hai, nhanh hai, hang hai
van hanh » van thanh, ban hanh, van anh
so sach » so sanh, bo sach, co sach
hai cua » thai cua, dai cua, hoi cua
nang du » nang tu, nang luc, nang doc
sach ky » sac ky, sach y, sach ty
luc van » luoc van, luu van, duc van
ve cau » va cau, ve cac, le cau
ke cau » ket cau
cua te » cua tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky ((nang dai) or (nang du)) hoi. hieu ((ve cau) OR (ke cau)) luc van hanh hai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky ((nang dai) OR (nang du)) hoi. hieu ((ve cau) OR (ke cau)) luc van hanh hai cua te*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky ((nang dai) or (nang du)) hoi. hieu ((ve cau) OR (ke cau)) luc van hanh hai cua te*".