SELECT SUM("dead") FROM table_204_514 WHERE "date" IN (1973, 1974)
how many people were killed in total in the attacks in 1973 and 1974 ?
CREATE TABLE table_204_514 (
    id number,
    "date" text,
    "sub" number,
    "flight" text,
    "dead" number,
    "hurt" number,
    "pax." number,
    "type" text,
    "perpetrator" text,
    "description" text
)