The psychologists David Marks and Richard Kammann attempted to replicate Russell Targ and Harold Puthoff's remote viewing experiments that were carried out in the 1970s at the Stanford Research Institute. In a series of 35 studies, they were unable to replicate the results so investigated the procedure of the original experiments. Marks and Kammann discovered that the notes given to the judges in Targ and Puthoff's experiments contained clues as to which order they were carried out, such as referring to yesterday's two targets, or they had the date of the session written at the top of the page. They concluded that these clues were the reason for the experiment's high hit rates. According to Terence Hines: