diff --git a/Makefile b/Makefile
index 0a1723b..eb38e46 100644
--- a/Makefile
+++ b/Makefile
@@ -36,6 +36,9 @@ watchpdf :
 watchscript :
 	while true; do ! make -s -q script && make script; sleep 0.5; done
 
+cleanplots:
+	for sd in $(SUBDIRS); do $(MAKE) -C $$sd/lecture cleanplots; done
+
 cleantex:
 	rm -f *~  $(BASENAME).aux $(BASENAME).log $(BASENAME).out $(BASENAME)-solutions.tex $(BASENAME).toc $(BASENAME).lo?  $(BASENAME).idx $(BASENAME)-term.i* $(BASENAME)-enterm.i* $(BASENAME)-code.i*
 	for sd in $(SUBDIRS); do $(MAKE) -C $$sd/lecture cleantex; done
diff --git a/README.fonts b/README.fonts
new file mode 100644
index 0000000..83bece0
--- /dev/null
+++ b/README.fonts
@@ -0,0 +1,23 @@
+Fonts for matplotlib
+--------------------
+
+Make sure the right fonts are installed:
+```
+sudo apt-get install ttf-lyx2.0 
+```
+There is some conflict with `lyx` fonts, so we first remove them
+and remove the matplotlib font cache:
+```
+sudo dpkg --remove --force-depends fonts-lyx
+rm ~/.cache/matplotlib/fontList.cache
+# rm ~/.matplotlib/fontList.cache     # older ubuntus
+```
+Then we need to plot something to recreate the matplotlib font cache:
+```
+make cleanplots
+make plots
+```
+To give back the fonts to lyx we reinstall them
+```
+sudo apt-get install fonts-lyx 
+```
diff --git a/chapter.mk b/chapter.mk
index e2f9044..d28642d 100644
--- a/chapter.mk
+++ b/chapter.mk
@@ -47,8 +47,9 @@ cleantex:
 	rm -f $(BASENAME).aux $(BASENAME).log
 	rm -f $(BASENAME)-chapter.aux $(BASENAME)-chapter.log $(BASENAME)-chapter.out $(BASENAME)-chapter.idx $(BASENAME)-solutions.tex $(BASENAME)-solutions.tex
 
+cleanplots: cleanpythonplots cleangnuplots
 
-cleanchapter : cleanpythonplots cleangnuplots cleantex
+cleanchapter : cleanplots cleantex
 
 
 cleanallchapter : cleanchapter
diff --git a/pointprocesses/lecture/pointprocessscetchA.eps b/pointprocesses/lecture/pointprocessscetchA.eps
index 9062460..15bfb45 100644
--- a/pointprocesses/lecture/pointprocessscetchA.eps
+++ b/pointprocesses/lecture/pointprocessscetchA.eps
@@ -1,7 +1,7 @@
 %!PS-Adobe-2.0 EPSF-2.0
 %%Title: pointprocessscetchA.tex
 %%Creator: gnuplot 4.6 patchlevel 4
-%%CreationDate: Mon Dec  2 10:40:01 2019
+%%CreationDate: Mon Dec  2 13:03:15 2019
 %%DocumentFonts: 
 %%BoundingBox: 50 50 373 135
 %%EndComments
@@ -433,7 +433,7 @@ SDict begin [
   /Author (benda)
 %  /Producer (gnuplot)
 %  /Keywords ()
-  /CreationDate (Mon Dec  2 10:40:01 2019)
+  /CreationDate (Mon Dec  2 13:03:15 2019)
   /DOCINFO pdfmark
 end
 } ifelse
diff --git a/pointprocesses/lecture/pointprocessscetchA.pdf b/pointprocesses/lecture/pointprocessscetchA.pdf
index b3f922b..afb0114 100644
Binary files a/pointprocesses/lecture/pointprocessscetchA.pdf and b/pointprocesses/lecture/pointprocessscetchA.pdf differ
diff --git a/pointprocesses/lecture/pointprocessscetchB.eps b/pointprocesses/lecture/pointprocessscetchB.eps
index 4300e2d..e543fa1 100644
--- a/pointprocesses/lecture/pointprocessscetchB.eps
+++ b/pointprocesses/lecture/pointprocessscetchB.eps
@@ -1,7 +1,7 @@
 %!PS-Adobe-2.0 EPSF-2.0
 %%Title: pointprocessscetchB.tex
 %%Creator: gnuplot 4.6 patchlevel 4
-%%CreationDate: Mon Dec  2 10:40:01 2019
+%%CreationDate: Mon Dec  2 13:03:15 2019
 %%DocumentFonts: 
 %%BoundingBox: 50 50 373 237
 %%EndComments
@@ -433,7 +433,7 @@ SDict begin [
   /Author (benda)
 %  /Producer (gnuplot)
 %  /Keywords ()
-  /CreationDate (Mon Dec  2 10:40:01 2019)
+  /CreationDate (Mon Dec  2 13:03:15 2019)
   /DOCINFO pdfmark
 end
 } ifelse
diff --git a/pointprocesses/lecture/pointprocessscetchB.pdf b/pointprocesses/lecture/pointprocessscetchB.pdf
index 8ede969..558282d 100644
Binary files a/pointprocesses/lecture/pointprocessscetchB.pdf and b/pointprocesses/lecture/pointprocessscetchB.pdf differ