Dyck context-free grammar formal definition?

I am searching information about the
"Dyck context free grammar". From
a small search I have done, it seems that
this grammar is a kind of balanced parenthesis
grammar, but I am not completelly sure.
Does anybody knows of any sitations explaing
"Dyck grammars" or a formal definition?

Also, how easy is to generate sentences from
its language?

Thanks in advance,

George