Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hoc hang » hoc hanh, hoc bang, hoc tang
hang hoa » hang khoa, thanh hoa, hang va
phan dan » phan dang, phan dau, nhan dan
doi tac » dong tac
doi tai » hoi tai, dai tai, moi tai
va phan » van phan, va phat, va phap
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 hang hoa hoc ma hoi va phan 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 hang hoa hoc ma hoi va phan dan.
• Adding a wildcard symbol may retrieve word variants: toc sach ((doi tac) or (doi tai)), nghien cuu mo hoc hang hoa hoc ma hoi va phan dan*.