PSM1 first attempt 80% close but not reached the target 85% any guidance

Hi
i gave an attempt today after seeing the

Mikhail Lapshin real mode consistenly 100% in test and open assesment scrum.org 100%. But when i appreaed the PSM1 exam i see questions are bit tricky resulted me to come close but not as expected.

i am bit disapointed to not able to clear in first attempt. i studied only 2016-Scrum-Guide-US (scrum.org) is there any other books i need to refer or mock tests

do let me know. Many thanks in advance for the advise

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Assessment: PSM I
Date: September 25, 2016 2:37:01 PM EDT

NOT PASSED
Score: 64 points scored (or 80.0%) out of 80 maximum points
__________________

Best Regards
Sekhar