Throughout life, all people are engaged in activities – practical or mental – trying to solve problems, activities that themselves give rise to problems. To solve these problems, people need knowledge. They can acquire this personal knowledge in two main ways. First, they can interrogate the world – natural and social – by means of closer observation, deeper analysis, controlled experiment, all forms of cognitive interaction. Second, they can enrich their personal knowledge by communicative interaction with the stock of public knowledge that mankind has built up over the millenia, thus acquiring what we may call information. The activities in which people engage also produce two other kinds of knowledge: that embodied in people (skills) and that embodied in their artefacts.

I would pinpoint 1958 as a special time in my career. I had for some years been working with the Classification Research Group in London, and in 1957 we had held a small but successful conference to which Jesse Shera, Gene Garfield and others had come from the USA. In 1958 I published my first book, Classification and Indexing in Science, and attended the International Conference on Scientific Information in Washington. This was my first visit to the USA - I flew in a US Army transport plane with . The Conference papers opened up all kinds of new information vistas - in many ways setting the agenda for the ensuing development of the field. I met many interesting people - some who stand out in the memory are Peter Luhn, , John O'Connor and Desmond Bernal. The experience of attending the conference, and of other visits I paid at that time, led to the writing of my second book, On Retrieval System Theory...

Neither citation nor loan demand is an adequate measure of literature use by a large community. Each is only an indicator, illuminating some aspects of use but with its own inherent bias. The joint study of several indicators gives a more balanced picture..