Hello Pablo and welcome to the Forum.
John Withers lists the following manuals for the Dragonfly in
his catalog.
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DRAGONFLY Maintenance Manual 55 pages Illustrated $24 CLA805
DRAGONFLY Spare Parts List 72 pages Fully Illustrated $24 CLA806
MILLER A. C. Electrical Equipment as fitted to the Douglas Dragonfly. Including Illustrated Spares List, Circuit Diagram and full Maintenance & Test Specifications. $7.50 CLA807
MILLER Maintenance & Running Instructions for A.C. Generator Set fitted to the Dragonfly, this booklet as originally supplied with machine. (Not as comprehensive as CLA 807) $6.00 CLA807A
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Details on how to purchase the manuals are provided in his post -
Douglas Motor Cycles Repro Books.
Please note the catalog shown in this post is from 2006. He has added new titles since then and prices and postage costs may have changed slightly. All prices are shown in Australian Dollars.
Dave