Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
van hanh » van thanh, ban hanh, van anh
tuc van » thuc van, truc van, tuc va
tang xa » trang xa, tang ma, lang xa
sach 7 » sach y
ve cac » va cac, vien cac
sach 2 » sach y
vi dau » vi dai, va dau, bi dau
ve cam » ve cham, va cam, ve cai

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach 7) OR (sach 2)) tang xa hoi. hieu ((ve cam) or (ve cac)) tuc van hanh vi dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach 7) OR (sach 2)) tang xa hoi. hieu ((ve cam) OR (ve cac)) tuc van hanh vi dau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach 7) OR (sach 2)) tang xa hoi. hieu ((ve cam) or (ve cac)) tuc van hanh vi dau tren".
• Adding a wildcard symbol may retrieve word variants: su ((sach 7) OR (sach 2)) tang xa hoi. hieu ((ve cam) or (ve cac)) tuc van hanh vi dau tren*.