Replaced some curly brackets with braces.

docs/rules.mk

@@ -8,9 +8,9 @@ docs: $(b)proposal.pdf $(b)presentation.pdf $(b)$(REPORT).pdf $(b)$(REPORT).bbl
 
 $(b)%.pdf: $(d)%.tex
 	mkdir -p $(@D)
-	TEXINPUTS=$(d): pdflatex ${PDFLATEX_FLAGS} $^
+	TEXINPUTS=$(d): pdflatex $(PDFLATEX_FLAGS) $^
 
 $(b)$(REPORT).bbl: $(d)$(REPORT).bib
 	BIBINPUTS=$(d) bibtex8 ${@:.bbl=.aux}
-	pdflatex ${PDFLATEX_FLAGS} $(d)$(REPORT).tex
-	pdflatex ${PDFLATEX_FLAGS} $(d)$(REPORT).tex
+	pdflatex $(PDFLATEX_FLAGS) $(d)$(REPORT).tex
+	pdflatex $(PDFLATEX_FLAGS) $(d)$(REPORT).tex