CREATE TABLE table_39520 ("Source" TEXT, "Date" TEXT, "DeSUS" TEXT, "Zares" TEXT, "NLPD" TEXT)

What is the source corresponding to a date of May 25 27?
SELECT "Source" FROM table_39520 WHERE "Date" = 'may 25–27'
SELECT "Source" FROM "table_39520" WHERE "Date" = 'may 25–27'