What is the magazine with the highest readership whose publisher is National Parks Conservation Association?
select ?ent where { ?ent wdt:P31 wd:Q41298 . ?ent wdt:P4295 ?obj . ?ent wdt:P123 wd:Q6974765 } ORDER BY DESC(?obj)LIMIT 5 
magazine: Q41298 national parks conservation association: Q6974765