pdf: generate thumbnails if ISABELLE_THUMBPDF set;
pdf: generate thumbnails if ISABELLE_THUMBPDF set;

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