Sir John Frederick Herschel and his invention/discovery of cyanotype:
Mike Ware: John Herschel’s Cyanotype: Invention or Discovery?
International Photography Hall of Fame: Sir John Frederick William Herschel
Kshitij Nagar: Sir John Herschel: How Photography Got Its Fix
Chemistry and Light: Cyanotype process
Anna Atkins
Encyclopaedia Britannica: Anna Atkins English Photographer and Botanist
The Guardian: Blue prints: photography pioneer Anna Atkins’s hand-crafted images – in pictures
see also references in: Cyanotype – In the footsteps of Anna Atkins
Prussian blue:
Amercan Chemical Society: Molecule of the Week – Prussian blue
Alexander Kraft: On the Discovery and History of Prussian blue
John Griswold: The Accidental Color That Changed The Course Of Art
Carlo Krier 