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| | Recommended Literature for the Penny Black and Penny Red |
 | | R.C. Alcock, The Alphabets of the British Line-Engraved Stamps, 2nd Edn., R.C. Alcock Ltd. Cheltenham, 1937 |
 | | Edward D. Bacon, Supplement to The Line-Engraved Postage Stamps of Great Britain Printed by Perkins, Bacon and Co., Chas. |
 | | Edward D. Bacon, The Essays, Proofs, Colour Trials and Reprints of the Line-Engraved Postage Stamps of Great Britain Printed by Perkins, Bacon and Co., Ltd., London, Chas. |
| www.home.earthlink.net /~pennyred/Lit.html (526 words) |
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