How many series originally aired before 1999 with more than 7 episodes and a DVD Region 1 release date of 16 april 2013?
CREATE TABLE "series" (
  "series_number" real,
  "number_of_episodes" real,
  "original_air_date" real,
  "dvd_region_2_release_date" text,
  "dvd_region_1_release_date" text
);
SELECT COUNT("series_number") FROM "series" WHERE "original_air_date"<1999 AND "number_of_episodes">7 AND "dvd_region_1_release_date"='16 april 2013';