Luxembourg Unofficial(?) Souvenir Sheets From 1945

Hi - I have these 2 Luxembourg souvenir sheets coming soon in an auction lot I won.
I'm guessing they are unofficial issues, since I didn't have any luck looking for Scott #'s.
Where to find info on these or sharing any experience running into them would be appreciated.
Thanks for looking!

Hi,

These items are not souvenir sheets but first day souvenir pages or souvenir leaflets (probably there are other terms in English), stamps affixed to a decorated page cancelled with first day of issue commemorative postmark.

These items are usually official, issued by the postal authorities (although, there are leaflets issued by private companies or collectors). They are not listed in the regular stamp catalogues like Scott, but I believe there are special catalogues for them.

Here is an example of such official souvenir from Germany (called in German: Ersttagsblatt), issued by the German post:

The top one has a first-day-of-issue cancellation. It is a first day sheet like the Ersttagsblatt shown by LaoPhil. The listing by Last Dodo:

https://www.lastdodo.com/en/items/9...Ni42MC4wLjA.

If you look at the bottom right of the second sheet, it says "Émis par la Vile de Luxembourg." This means "Issued by the City of Luxemburg." It is a commemorative sheet (note: not to be confused with commemorative or souvenir stamp sheet as I expect LaoPhil referred to). The stamps were issued 6 November 1944, almost a year before the date of the cancel.

https://www.lastdodo.com/en/items/9...Ni42MC4wLjA.

Thank you both for taking the effort to explain... okay, that helps me understand the different kinds of souvenir sheets/pages.and first day or commemorative cancels now.