Tourism to the area became more common after Pripyat was featured in popular video games ' and '. Fans of the "S.T.A.L.K.E.R." franchise, who refer to themselves as "stalkers", often gain access to the Zone. (Both the name "the Zone" and the term "stalker" derive from Arkady and Boris Strugatsky's book "Roadside Picnic", which predates the Chernobyl disaster but describes a similar setting.) Prosecution of trespassers became more severe after a significant increase in trespassing in the Exclusion Zone. An article in the penal code of Ukraine was specially introduced, and horse patrols were added to protect the zone's perimeter.