from http://www2.ncsu.edu/ncsu/pams/physics/Edu_Resources/demoroom/manual/EandM/Demos/H1030.html


from http://www.astro.uva.nl/michielb/sun/vlekfig.htm


from http://argo.tuc.noao.edu/~keller/solis/now.html


from http://www.kis.uni-freiburg.de/~steffan/magnet.html


from http://www.gaussbusters.com/ppm93.html