Perhaps you should try some spelling variations:
ninh viet » sinh vien, anh viet
toc sach » hoc sach, doc sach, thuoc sach
van ninh » van minh, van dinh, van binh
sach ty » sach y, sach tu, sach thu
ca tren » cau tren, la tren, co tren
duc van » duc va, duc tan, duc manh
cac duc » cac du, cao duc, cac dac
hieu ve » hieu va, hieu van
tang ma » mang may, tang van
xang ma » nang ma, sang ma, rang ma
cu tren » tu tren, dua tren
ve cac » va cac, vien cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ty ((xang ma) or (tang ma)) hoa. hieu ve cac duc van ninh viet ((ca tren) OR (cu tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ty ((xang ma) OR (tang ma)) hoa. hieu ve cac duc van ninh viet ((ca tren) OR (cu tren))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ty ((xang ma) or (tang ma)) hoa. hieu ve cac duc van ninh viet ((ca tren) OR (cu tren))*".