The answer is: true.
An open book test, contrary to what common sense would dictate, is not an easier kind of test. In fact, because bibliographical resources can be referenced, the quality standards demanded of the answers might actually be more challenging, not to mention that time will be measured and it could be a determining factor in your capacity to finish the test. For those reasons, it is wise to bring the information or data that is permitted during the test in an organized fashion, be that thematically, chronologically or otherwise (however your memory and your retrieval capacity work best in tandem).