Born 1943 in Lausanne, I am a bilingual person F-D with mother tongue (Swiss-) German (dialect) but preferring French language. English is a foreign language for me, so I might not always find the right words in it. I have been an informatician for 38 years and have a math. degree (F: licence ès sciences math.)... My math. interests are on all basics up to advanced level themes. For me, the literature of the group N. Bourbaki is often best choice, but not always. Currently I am self-studying their Théories spectrales (chapt. 1 & 2, I haven't seen later ones yet) after Espaces vectoriels topologiques. But I jumped over the subject of holomorphic symbolic calculus (also called 'functional' instead of 'symbolic') which I preferred to study (for one variable) in Walter Rudin's Functional Analysis that covers much out of the subjects contained in the mentioned two Bourbaki books. Moreover the chapter (12) of this in which I am now (Dec.2022) has - as far as I know - not yet its equivalent in Bourbaki literature: it is about Bounded Operators on a Hilbert Space ... This Rudin book gave me problems for - some of - which I set up questions here. While I am writing this, the background of my problem is the competition between two measure theories, one of which is still dominating (seemingly even in French math.) while I prefer the other one (found in Bourbaki's Integration) ...