CREATE TABLE table_23545 ("No. in series" FLOAT, "No. in season" FLOAT, "Title" CLOB, "Directed by" CLOB, "Written by" CLOB, "U.S. viewers  ( million ) " CLOB, "Original air date" CLOB, "Production code" FLOAT)

Who wrote episode number 48
SELECT "Written by" FROM table_23545 WHERE "No. in series" = '48'
SELECT "Written by" FROM "table_23545" WHERE "No. in series" = '48'