Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
ban hang » ngan hang
dang cay » dang xay, dang ca, dang cac
cay phoi » cap phoi, tay hoi, cay cho
hieu van » hieu va, thien van, lieu va
cam cac » ca cac, cam chan
vai cua » dai cua, hai cua, lai cua
nam cac » nam cao, nam sach
cua te » cua tu
y dang » ky dang, 2 dang, _ dang

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

• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach y dang cay phoi. hieu van ((cam cac) OR (nam cac)) ((ban hanh) OR (ban hang)) vai cua te~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach y dang cay phoi. hieu van ((cam cac) or (nam cac)) ((ban hanh) OR (ban hang)) vai cua te~".
• Adding a wildcard symbol may retrieve word variants: doc sach y dang cay phoi. hieu van ((cam cac) or (nam cac)) ((ban hanh) OR (ban hang)) vai cua te*.