to be printed separately and either bound in or tipped in with an adhesive. Frederic E. Ives is usually credited with the first commercially successful process that was compatible with ordinary letterpress printing, so that halftone blocks could be printed along with blocks of text in books, periodicals and newspapers. His process came into widespread use during the 1890s, largely replacing the hand-engraved wood and metal blocks that had previously served to provide illustrations. As in many other fields of invention, there are conflicting claims of priority, instances of simultaneous invention, and variously nuanced definitions of the terminology, so sorting out the merits of the "first" claims made on behalf of the many inventors in the field of halftone reproduction—not infrequently biased by nationalistic sentiments—can be very problematic. See also Photogravure References Further reading Harry Jenkins, Stephen H. Horgan, Frederic Eugene Ives, Containing Practical Instructions for Producing Photoengraved Plates... , Chicago 1902. Engraving Photographic processes dating from the 19th century et:Fotogravüür