'Switzerland', file of M S Bartlett Correspondence with A M Herzberg of Imperial College of Science and Technology about MS Bartlett's contribution to a volume in honour of Dr Yates' 80th birthday, and letter from Niels Keiding about stochastic population processes in random environments. The file also contains a draft of paper 'Some stochastic models in biology', a draft of paper 'On doubly stochastic population processes', and loose notes and calculations, including on switching models and doubly stochastic population process. 1981