Outlines methods and knowledge for self-taught language acquisition. Ex­clu­sive­ly free and freely and directly accessible content, web dictionaries and free software are discussed. In addition, the possibilities of extended lan­guage study with native speakers are presented, for language tandems lo­cal­ly and via the internet. All articles include extensive link lists and training rec­om­men­da­tions for further study of the topics covered.

Referenced in: Omniglot the online encyclopedia of writing systems and languages  • The Kitti­wake Trust Multilingual Library

Cryptographic checksums (electronic fingerprints) are used to ensure the tech­nical and content integrity of your documents. In addition, cryptographic sign­ing with OpenPGP can provide your documents, messages, and e-mails with verifiable personal proof of authenticity. If you then publish the public key cer­tifi­cate on your official website, for example, every reader and cor­re­spond­ence partner can have a signature verification performed fully automatically in the background, e.g. via their e-mail program.

This increases protection against identity misuse and identity theft; any read­er can then verify whether a message actually originates from you. The Open­PGP encryption standard also allows you to send your messages and docu­ments (e.g. manuscripts, negotiation correspondence, draft contracts) en­crypted.

Referenced in: “Künstliche Intelligenz - Ethik und Recht”, Hoeren/Pinelli (Hrsg.), 2022, footnote 49 on page 11, Verlag C.H. Beck, (book review by Roland Kemper) • “M2M-Geschäfte, Vertragsschluss und vertragliche Struk­tu­ren im automatisierten E-Procurement”, Dajana Mohr, Tectum Verlag 2022, footnote 283 on page 72, PDF sample  •  German legal magazine JuristenZeitung, 18.09.2020, “Daten im Rechtsverkehr – Überlegungen für ein allgemeines Datenvertragsrecht” (footnote 14, page 881), Thomas Hoeren and Stefean Pinelli, Verlag Mohr Siebeck  •  Wikipedia article “Checksum” (EN) • Wikipedia article “Prüfsumme”  • 
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Word processing, writing science literature, book creation, graphical desktop pub­lish­ing, web PDF documents, e-book writing, and a mini-introduction to cre­ating web pages.

Typesetting programs offer extremely extensive design possibilities, the ef­fec­tive use of which requires a longer training period. Free software that is stable over the long term proves to be advantageous here, since changes to op­er­at­ing and functional concepts occur as part of a natural development, in con­trast to proprietary software where a continuous new purchase of products and operating manuals is often artificially forced. (Operating system) platform in­de­pend­ence as well as the mastery of a truly open document format suit­able for archiving are further central criteria, especially for use in hetero­geneous company computer networks and in the administration area. High-quali­ty typesetting is possible even with old and very old computers, thanks to spe­cial­ized lightweight free operating systems and programs.

This overview introduces you to widely used free typesetting systems and ba­sic document types. Extensive link lists lead to further, equally powerful free pro­gram alternatives.

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Explanation of basic terms in the field of free software, with short portraits of popu­lar free operating systems. Furthermore, it is illustrated how old com­put­ers can be turned into powerful desktop com­put­ers with the help of spe­cial­ized distributions.

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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. 13 pages:   A4  •  A4 duplex  •  US-Let­ter  •  US-Letter duplex

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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)..