SITES ABOUT PAPER WATERMARKS:
Bernstein - The Memory of Paper and survey of known paper databases.
The Corpus database of Spanish watermarks at the Instituto de Patrimonio Cultural de España (IPCE).
Filigranes and Watermarks blog by Antonio de la Cruz.
Papel y filigranas (Restoration Workshop at the Monastery of Sant Pere de les Puel·les).
The Thomas L. Gravell Watermark Archive and The First International Conference on the History, Function, and Study of Watermarks (Roanoke, 10-13 October 1996).
The WWW Watermark Archive Initiative by Prof. Robert W. Allison.
Le filigrane degli archivi genovesi.
Digital Watermark & Ornament Catalogue (Paper Used By William Stansby in the Jonson Folio).
Watermarks and Watermarks Lesson at the Robert C. Williams Paper Museum (formerly American Museum of Papermaking, AMP), of the Renewable Bioproducts Institute at Georgia Tech (formerly Institute of Paper Science and Technology, IPST).
Watermark images at the British Association of Paper Historians (BAPH).
The Watermark Collection of Stefan Feyerabend; Stefan Feyerabend Maschinenwasserzeichenpapiere.
Handmade paper / Watermarks by Dieter Freyer.
Watermarks in Incunabula printed in the Low Countries (WILC) at the National Library of the Netherlands.
Wasserzeichen des Mittelalters (WZMA).
Watermark Database of the Dutch University Institute for Art History.
Paper Identification Database at the Finnish National Archives.
Watermark Registration Standard and Classification at the International Association of Paper Historians (IPH).
Dard Hunter at Dard Hunter Studios, at The Friends of Dard Hunter and at the Robert C. Williams Paper Museum.
Watermark and Marca al agua at the Wikipedia.
History and samples of Whatman papers and another antique art papers at the Paper Collection in The Virtual Museum of Watercolor Materials of The Whimsie Studio.
Digital Imaging of Watermarks at Earlypaper.com.
Watermark Papermaking at Eastern Fine Paper.
ORGANIZATIONS AND SITES WITH LINKS ABOUT PAPER IN GENERAL:
Asociación Hispánica de Historiadores del Papel (AHHP).
Paper Collections, Watermark Databases and National Organizations at the International Association of Paper Historians (IPH).
Links to Related Websites at the British Association of Paper Historians (BAPH).
Webguide to the world of handmade paper: Dieter Freyer: Büttenpapier.
Paper and Papermaking at the Book Information Website.
Links to other papermaking web sites at the Robert C. Williams Paper Museum.
Sites relating to the history of paper and technology in the information about the title by John Balston on James Whatman.
Individual Watermarks by Favini.
Examples of Watermarks and How to Watermark in the All About Paper section of the Conqueror website.
Confessions of a Filigranophile by Paul C. LoCasto.
Watermarks in Handmade Paper by Gail Stiffe.