My name is Bob Andriesse. I am a dutch physicist who was self employed for almost 40 years and I have a passion for mathematics.
One reference I can give you is an electronics article I wrote in french ( I am sorry) which is still available on my (ex)website. The web site is not maintained anymore, because the french branch was closed, but I kept my mail address firstname.lastname@example.org.
The article is: http://www.smartec.fr/intl/docs/apputi12fr.pdf