File:Blackboard bold in typewritten notes from Narasimhan (1966).png

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Summary[edit]

Media data and Non-free use rationale
Description	Part of a page from Narasimhan (1966), a set of typewritten lecture notes which were published directly as provided by the author, apparently typed on an IBM Selectric typewriter. This portion shows the mixture of hand-written and type-written symbols, along with a rare appearance of "blackboard bold" style letters for R and C, new at the time but now pervasive in technical literature. Narasimhan, Raghavan (1966). Introduction to the Theory of Analytic Spaces. Lecture Notes in Mathematics. Springer. p. 9. doi:10.1007/bfb0077071
Author or copyright owner	Raghavan Narasimhan
Source (WP:NFCC#4)	Screenshot of Springer's scan of the book
Date of publication	1966
Use in article (WP:NFCC#7)	Blackboard bold
Purpose of use in article (WP:NFCC#8)	This is an illustrative image showing a typewritten document from the 1960s near the beginning of the use of 'blackboard bold' type in mathematics.
Not replaceable with free media because (WP:NFCC#1)	The software or website from which the screenshot is taken is copyrighted and not released under a free license, so creation of a free image is not possible.
Not replaceable with textual coverage because (WP:NFCC#1)	Any available document published in the 1960s is going to be copyrighted.
Minimal use (WP:NFCC#3)	This is just a small decontextualized snippet of some mathematical lecture notes. It is not commercially interesting in and of itself. The resolution can't be much lower or the symbols will start to become illegible.
Respect for commercial opportunities (WP:NFCC#2)	The use of a low resolution screenshot from software or a website will not impact the commercial viability of the software or site.
Fair useFair use of copyrighted material in the context of Blackboard bold//en.wikipedia.org/wiki/File:Blackboard_bold_in_typewritten_notes_from_Narasimhan_(1966).pngtrue

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File history

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	Date/Time	Thumbnail	Dimensions	User	Comment
current	02:03, 26 July 2023		826 × 602 (142 KB)	Jacobolus (talk \| contribs)	this image was reduced to a resolution where it no longer illustrates the topic
	00:02, 26 July 2023	No thumbnail	370 × 269 (64 KB)	DatBot (talk \| contribs)	Reduce size of non-free image (BOT - disable)
	09:51, 25 July 2023	No thumbnail	826 × 602 (142 KB)	Jacobolus (talk \| contribs)	somewhat lower resolution
	09:32, 25 July 2023	No thumbnail	1,652 × 1,204 (294 KB)	Jacobolus (talk \| contribs)	Uploading an excerpt from a non-free work using File Upload Wizard

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Blackboard bold

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Horizontal resolution	56.69 dpc
Vertical resolution	56.69 dpc