Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
sach tru » sach truc, sach thu, sach tu
tru nang » tra nang, tri nang, truc nano
hieu van » hieu va, thien van, lieu va
dieu tra » dieu tri, dieu cua
van cac » van hac, van cau, van bac
duc ban » duc van, dua ban, duc man
x hoi » xa hoi, o hoi, x ho

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 tru nang x hoi. hieu van cac ((duc ban) or (duc tan)) than ((dieu tra) or (kiem tra)) te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach tru nang x hoi. hieu van cac ((duc ban) OR (duc tan)) than ((dieu tra) OR (kiem tra)) te.
• Adding a wildcard symbol may retrieve word variants: thu sach tru nang x hoi. hieu van cac ((duc ban) or (duc tan)) than ((dieu tra) or (kiem tra)) te*.