Document integrity: Practical Application of Cryptographic Checksums, with an introduction to applied cryptography.
Referenced in: German legal magazine JuristzenZeitung, 18.09.2020, “Daten im Rechtsverkehr”, footnote 14, page 881 • M2M-Geschäfte, Vertragsschluss und vertragliche Struk­tu­ren im automatisierten E-Procurement”, footnote 283 on page 72 • WP article “Prüfsumme • WP article “Checksum” (EN) • Top 10 • Top 10 (EN) • Top 10

Scientific typesetting: Free Typesetting Software for the Professional Document Preparation Top 10 • Top 10 (EN)

Introduction to the indirect proof: Proof of the Irrationality of the Square Root of 2 Top 10 • Top 10 (EN)

Mathematical proofs are used to prove the cor­rect­ness of formulas and assumed facts. Sev­er­al basic procedures and ways of veri­fy­ing mathematical correctness are in use, all of which follow a fixed scheme.

For the proof of the irrationality of the square root of 2 dif­fer­ent proofs exist. This article explains the indirect proof vari­ant in detail and introduces one of the possible short spell­ings in mathematical notation. Exercises with solutions con­soli­date what has been learned. 12 pages::

      A4  •  A4 duplex  •  US-Letter  •  US-Letter duplex

School mathematics: Detailed so­lu­tions to the first 27 text problems of A first book in Al­­ge­­bra, author Wallace C. Boyden, added, a textbook for be­gin­ners in algebra: Text problems with solutions, 10 pages (PDF, A4 format, in English)..

Web book in five chapters, for self-study of a language:: Study of Languages with Computer and Internet”. German version: Sprachstudium mit Computer und Weltnetz
Referenced in: Omniglot the online encyclopedia of writing systems and languages  • The Kittiwake Trust Multilingual Library

Software equipment: Introduction to Free Software and Operating Systems
Existing computer works but is no longer fast enough for current software and operating systems? Use free, 100 % free of charge, continuously maintained and security updated specialized operating system distributions for new, for old and for ancient computers, article section: Modern operating systems for old computers Top 10

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Freiburg i.Br.: Freiburg Excursion Destinations and Film Recommendations
Presents many of the most beautiful Youtube videos on excursion destinations in and around Freiburg.
Referenced in: WP article “Freiburg im Breisgau” (EN) • WP article “Fribourg-en-Brisgau” (FR)

Holistic reality structures described in film, TV and literature: Inner Levels of Communication and Reality Structures, contains many references to Youtube videos.

As of: November 19, 2022

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