Referee's report by Edward Arthur Milne, on a paper 'Time-lag in a control system' by A Callender, Douglas Rayner Hartree and A Porter Sectional committee: Mathematics Recommended for publication in Philosophical Transactions. The paper is long but there seems to be no way of abbreviating it. It is difficult to understand, so it could be amended. The main problem is understanding the equations. [Published in Philosophical Transactions A, 1936]. Endorsed on verso as received 7 August 1935. August 1935