TEXSRC  = $(wildcard blatt*.tex)
TEXTRG  = $(TEXSRC:%.tex=%.pdf)

.PHONY: all clean

all: $(TEXTRG)

clean:
	-rm -f blatt*.pdf blatt*.log blatt*.aux

RERUN_REGEX = "(There were undefined references|Rerun to get .* right)" 
%.pdf: %.tex
	pdflatex $<
	egrep $(RERUN_REGEX) $(@:%.pdf=%.log) >/dev/null && pdflatex $<; true