Table: eternal_derby_croatia_2
Columns: date
competition
ground
score
attendance
report

Question: What is the total attendance with a Report of sd.hr, and a Score of 3–1, and a Date of 14 apr 2001?
SQL: SELECT SUM("attendance") FROM eternal_derby_croatia_2 WHERE "report" = 'sd.hr' AND "score" = '3–1' AND "date" = '14 apr 2001'