clarified ISABELLE_DOC_FORMAT -- eliminated slightly odd fall-back;
clarified ISABELLE_DOC_FORMAT -- eliminated slightly odd fall-back;

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle