The book is written in the Greek language  
 Το έκτο κλειδί
For more information about its presentation and some excerpts (in Greek language):
Go to the Greek Home page                            and then 
navigate to  Παρουσίαση βιβλίου   (Book presentation) for the 
specific book       
The sixth key
Detective story 
ISBN 978-618-82752-7-0
293 Σελίδες Α5
Available in PDF and EPUB format on websites :
EPUB & PDF 
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The book, in electronic form, is also available (free of charge) by the author. You can order it from the "CONTACT" page following simple instructions.