John R. C. Martyn Books

Andre De Resende on court life

By Andre De Resende

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Juvenal

By John R. C. Martyn

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Pope Gregory s letter bearers

By John R. C. Martyn

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"With the Lombards invading Italy, and Slavs invading Illyria, and very active slave-dealers at work, the number of men and women who reached Rome and carried a papal letter, to sort out a legal or...

The siege of Mazagao

By John R. C. Martyn

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Gregory and Leander

By John R. C. Martyn

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"The book aims to reveal the hitherto totally unexamined relationship between these two most admirable and most courageous men, two really close friends who played major parts in establishing the o...

How to Convert ISBN-10 to ISBN-13 (and Vice Versa): A Complete Guide

If you’re in the world of books—whether as a publisher, librarian, bookseller, or avid collector—you’ve likely come across the terms ISBN-10 and ISBN-13. Understanding these formats and knowing how to convert between them is essential for maintaining consistency and compatibility in book records. In this post, we’ll cover everything you need to know about ISBN conversions, step by step.

What is an EAN and How Does it Relate to an ISBN?

If you’ve ever purchased a product online or in a store, you’ve likely come across a barcode. Behind these barcodes lies a standardized system that makes modern commerce possible. Two key codes often encountered are the EAN (European Article Number) and ISBN (International Standard Book Number). But what are they, how are they connected, and why are they so crucial? Let’s explore.