A huge number of donations to political parties came from unknown sources over the last four years -- a practice the Election Commission has been trying to discourage. More than 3,000 donations in this period came without donors' details like Permanent Account Number (PAN) or addresses, said the Delhi-based think tank, Association of Democratic Rights or ADR, in a report. Political parties are required to submit details of donors who have made donations above Rs. 20,000 in a financial year to the Election Commission every year.