Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
cau tren » cu tren, dau tren, ca tren
dat tren » dat trong, dua tren
dang xa » dang xay, lang xa, dang ha
sach o » sach lo, sac o, sach y
o dang » xo dang, do dang, so dang

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach o dang xa hoi. hieu van ((pham duc) or (cam xuc)) van hanh vi ((cau tren) or (dat tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach o dang xa hoi. hieu van ((pham duc) OR (cam xuc)) van hanh vi ((cau tren) OR (dat tren)).
• Adding a wildcard symbol may retrieve word variants: thu sach o dang xa hoi. hieu van ((pham duc) or (cam xuc)) van hanh vi ((cau tren) or (dat tren))*.