SELECT "Written by" FROM table_73892 WHERE "Original air date" = 'January 13, 1999'
The episode with original air date January 13, 1999 is written by who?
CREATE TABLE table_73892 (
    "No. in series" real,
    "No. in season" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" text
)