Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
dua tren » dung tren
van hanh » van thanh, ban hanh, van anh
duc van » duc va, duc tan, duc manh
cac duc » cac du, cao duc, cac dac
sach ky » sach y, sach ty, sach kem
tang xa » trang xa, tang ma, lang xa
hieu va » lieu va, hieu qua
sac ky » cac ky, sai ky

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 ky) OR (sac ky)) tang xa hoi. hieu va cac duc van hanh vi ((dua tren) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ky) OR (sac ky)) tang xa hoi. hieu va cac duc van hanh vi ((dua tren) OR (cau tren))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach ky) OR (sac ky)) tang xa hoi. hieu va cac duc van hanh vi ((dua tren) or (cau tren))*".