CREATE TABLE table_60797 ("Battle" TEXT, "Date" TEXT, "Bulgarian Commander" TEXT, "Byzantine Commander" TEXT, "Result" TEXT)

What is the Byzantine Commander with a Bulgarian Victory at the Siege of Lovech?
SELECT "Byzantine Commander" FROM table_60797 WHERE "Result" = 'bulgarian victory' AND "Battle" = 'siege of lovech'
SELECT "Byzantine Commander" FROM "table_60797" WHERE "Battle" = 'siege of lovech' AND "Result" = 'bulgarian victory'