Two simple proofs in PDE theory

In PostScript format

For A4 paper, in 300 dpi (dots per inch) or 600 dpi resolution.

In DVI format

For A5 paper.

To print on A4 paper like the above PostScript files, you may do as follows on a unix machine (if it has dvidvi and dvips):
dvidvi -m '2:0(-0mm,-0mm),1(148mm,0mm)' etc-a5.dvi
dvips -t landscape

Please respect the copyright. The note may be freely copied for personal or classroom use; contact me if you wish to copy them for any other reason.