Letter from F D Drake, Director, AIO [Arecibo Ionospheric Observatory], to Dr J F R Gower, Department of Physics, University of Cambridge, Cambridge, England Says that they would be pleased to have Dr Gower and his wife visit Arecibo on their trip. Warns Dr Gower that the AIO is quite difficult to reach and is a two and half hour drive from San Juan on quite difficult roads. 20 September 1967