complete this disguise, Clark avoids violent confrontation, preferring to slip away and change into Superman when danger arises, and in older stories he would suffer occasional ridicule for his apparent cowardice. In Superboy #78 (1960), Superboy makes his costume out of the indestructible blankets found in the ship he came to Earth in. In Man of Steel #1 (1986), Martha Kent makes the costume from human-manufactured cloth, and it is rendered indestructible by an "aura" that Superman projects. The "S" on Superman's chest at first was simply an initial for "Superman". When writing the script for the 1978 movie, Tom Mankiewicz made it Superman's Kryptonian family crest. This was carried over into some comic book stories and later movies, such as Man of Steel. In the comic story Superman: Birthright, the crest is described as an old Kryptonian symbol for hope. Clark works as a newspaper journalist. In the earliest stories, he worked for The Daily Star, but the second episode of the radio serial changed this to the Daily Planet. In comics from the early 1970s, Clark worked as a television journalist (an attempt to modernize the character). However, for the 1978 movie, the producers chose to make Clark a newspaper journalist again because that was how most of the public thought of him. The first story in which Superman dies was published in Superman #149 (1961), in which he is murdered by Lex Luthor by means of kryptonite. This story was "imaginary" and thus was ignored in subsequent books. In Superman #188 (April 1966), Superman is killed by kryptonite radiation but is revived in the same issue by one of his android doppelgangers. In the 1990s The Death and Return of Superman story arc, after a deadly battle with Doomsday, Superman died in Superman #75 (Jan. 1993). He was later revived by the Eradicator using Kryptonian technology. In Superman #52 (May 2016) Superman is killed by kryptonite poisoning, and this time he is not resurrected, but replaced by the Superman of an alternate timeline. Superman maintains a secret hideout called the "Fortress of Solitude", which is located somewhere in the Arctic. Here, Superman keeps a collection of mementos and a laboratory for science experiments. In Action Comics #241, the Fortress of Solitude is a cave in a mountain, sealed with a very heavy door that is opened with a gigantic key too heavy for anyone but Superman to