The sentence containing two quotations and that is such that (a) if you replace each quotation in it with an asterisk you get the text
"The sentence containing two quotations and that is such that (a) if you replace each quotation in it with an asterisk you get the text * and (b) each quotation in it is of the text * is unprovable."
and (b) every quotation in it is of the text
"The sentence containing two quotations and that is such that (a) if you replace each quotation in it with an asterisk you get the text * and (b) each quotation in it is of the text * is unprovable."
is unprovable.
