What types of obstacles do historians have to overcome?

Historians have to overcome problems such as false reports of events and destroyed evidence. They can overcome these by source checking all evidence with other verified accounts. Some of the calculations can be incorrect and falsehood can be spread. So they have to act like a detective to make sure their information is correct. Ways to get information is through research of similar events. Also they may investigate the site where the event occurred such as in wars or natural disasters. So they have to discuss with other historian, because they all can have different points of view.