update comments

conf/ezbookkeeping.ini

@@ -301,11 +301,11 @@ custom_map_tile_server_default_zoom_level = 14
 
 [exchange_rates]
 # Exchange rates data source, supports the following types:
-# "euro_central_bank"
-# "bank_of_canada"
-# "reserve_bank_of_australia",
-# "czech_national_bank"
-# "national_bank_of_poland"
+# "euro_central_bank": https://www.ecb.europa.eu/stats/policy_and_exchange_rates/euro_reference_exchange_rates/html/index.en.html
+# "bank_of_canada": https://www.bankofcanada.ca/rates/exchange/daily-exchange-rates/
+# "reserve_bank_of_australia": https://www.rba.gov.au/statistics/frequency/exchange-rates.html
+# "czech_national_bank": https://www.cnb.cz/en/financial-markets/foreign-exchange-market/central-bank-exchange-rate-fixing/central-bank-exchange-rate-fixing/
+# "national_bank_of_poland": https://nbp.pl/en/statistic-and-financial-reporting/rates/
 data_source = euro_central_bank
 
 # Requesting exchange rates data timeout (0 - 4294967295 milliseconds)