Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hoc tang » hoc bang, hoc tan, hoc tieng
tang hoa » hang hoa, tang ha, tang ho
nhan dan » phan dau, gian dan, nhan tai
doi tac » dong tac
doi tai » hoi tai, dai tai, moi tai
va nhan » van nhan, ca nhan, va phan
mo hoc » mon hoc, co hoc
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ((doi tac) or (doi tai)), nghien cuu mo hoc tang hoa hoc ma hoi va nhan dan~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((doi tac) OR (doi tai)), nghien cuu mo hoc tang hoa hoc ma hoi va nhan dan.
• Adding a wildcard symbol may retrieve word variants: toc sach ((doi tac) or (doi tai)), nghien cuu mo hoc tang hoa hoc ma hoi va nhan dan*.