In 1938, Ehrenfried Pfeiffer's text, "Bio-Dynamic Farming and Gardening", was published in five languages – English, Dutch, Italian, French, and German; this became the standard work in the field for several decades. In July 1939, at the invitation of Walter James, 4th Baron Northbourne, Pfeiffer travelled to the UK and presented the Betteshanger Summer School and Conference on Biodynamic Farming at Northbourne's farm in Kent. The conference has been described as the 'missing link' between biodynamic agriculture and organic farming because, in the year after Betteshanger, Northbourne published his manifesto of organic farming, "Look to the Land", in which he coined the term 'organic farming' and praised the methods of Rudolf Steiner. In the 1950s, Hans Mueller was encouraged by Steiner's work to create the organic-biological farming method in Switzerland; this later developed to become the largest certifier of organic products in Europe, "Bioland".