diff --git a/source/conf.php b/source/conf.php
index fbd147f..95ce744 100644
--- a/source/conf.php
+++ b/source/conf.php
@@ -2,6 +2,8 @@
 
 namespace davina\conf;
 
+require_once(DIR_LOGIC . '/helpers/list.php');
+
 
 /**
  */
@@ -26,6 +28,7 @@ class struct_source_data_ics_feed
  */
 class struct_source
 {
+	public string $name;
 	public string $kind;
 	public $data;
 }
@@ -44,7 +47,10 @@ class struct_settings
 class struct_root
 {
 	public struct_auth $auth;
-	public struct_source $source;
+	/**
+	 * @var array {list<struct_source>}
+	 */
+	public array $sources;
 	public struct_settings $settings;
 }
 
@@ -57,6 +63,18 @@ class _state
 }
 
 
+/**
+ */
+function validate_source_name(
+	string $source_name
+) : string
+{
+	$matchs = null;
+	$result = preg_match('/^[0-9a-zA-Z]+$/', $source_name, $matches);
+	return ($result === 1);
+}
+
+
 /**
  */
 function load(
@@ -78,12 +96,29 @@ function load(
 			$auth->data = (($data_raw['auth'] ?? [])['data'] ?? null);
 			$data->auth = $auth;
 		}
-		// source
+		// sources
 		{
-			$source = new struct_source();
-			$source->kind = $data_raw['source']['kind'];
-			$source->data = ($data_raw['source']['data'] ?? null);
-			$data->source = $source;
+			$sources = [];
+			/**
+			 * @todo check for name duplicates
+			 */
+			$data->sources = \davina\helpers\list_\map(
+				$data_raw['sources'],
+				function ($source_raw) {
+					if (! validate_source_name($source_raw['name']))
+					{
+						throw (new \Exception(\sprintf('invalid source name: "%s"', $source_raw['name'])));
+					}
+					else
+					{
+						$source = new struct_source();
+						$source->name = $source_raw['name'];
+						$source->kind = $source_raw['kind'];
+						$source->data = ($source_raw['data'] ?? null);
+						return $source;
+					}
+				}
+			);
 		}
 		// settings
 		{
diff --git a/source/helpers/list.php b/source/helpers/list.php
new file mode 100644
index 0000000..89a59c1
--- /dev/null
+++ b/source/helpers/list.php
@@ -0,0 +1,35 @@
+<?php
+
+namespace davina\helpers\list_;
+
+
+/**
+ */
+function map(
+	array $list,
+	\Closure $function
+) : array
+{
+	return \array_map(
+		$function,
+		$list
+	);
+}
+
+
+/**
+ */
+function filter(
+	array $list,
+	\Closure $predicate
+) : array
+{
+	return \array_values(
+		\array_filter(
+			$list,
+			$predicate
+		)
+	);
+}
+
+ ?>
diff --git a/source/main.php b/source/main.php
index c4b4bdd..7bf36c2 100644
--- a/source/main.php
+++ b/source/main.php
@@ -22,19 +22,29 @@ function main(
 	
 	\date_default_timezone_set(\davina\conf\get()->settings->timezone);
 	
-	$source = \davina\sources\make(
-		[
-			'kind' => \davina\conf\get()->source->kind,
-			'data' => \davina\conf\get()->source->data,
-		]
-	);
+	/**
+	 * @todo nicht einfach die source names als keys verwenden …
+	 */
+	$sources = [];
+	foreach (\davina\conf\get()->sources as $source_raw)
+	{
+		$sources[$source_raw->name] = \davina\sources\make(
+			$source_raw->kind,
+			$source_raw->data
+		);
+	}
 	
-	$principal_backend = new \davina\overwrites\class_principle_backend();
+	$principal_backend = new \davina\overwrites\class_principle_backend($sources);
 	
 	$server = new \Sabre\DAV\Server(
 		[
-			new \Sabre\CalDAV\Principal\Collection($principal_backend),
-			new \Sabre\CalDAV\CalendarRoot($principal_backend, new \davina\overwrites\class_caldav_backend($source)),
+			new \Sabre\CalDAV\Principal\Collection(
+				$principal_backend
+			),
+			new \Sabre\CalDAV\CalendarRoot(
+				$principal_backend,
+				new \davina\overwrites\class_caldav_backend($sources)
+			),
 		]
 	);
 	
@@ -42,12 +52,8 @@ function main(
 	
 	$server->addPlugin(
 		new \Sabre\DAV\Auth\Plugin(
-			\davina\overwrites\make_auth_backend(
-				$source,
-				[
-					'kind' => \davina\conf\get()->auth->kind,
-					'data' => \davina\conf\get()->auth->data,
-				]
+			new \davina\overwrites\class_auth_backend_basic(
+				$sources
 			)
 		)
 	);
diff --git a/source/overwrites/auths/basic.php b/source/overwrites/auths/basic.php
index 6d42754..cee97aa 100644
--- a/source/overwrites/auths/basic.php
+++ b/source/overwrites/auths/basic.php
@@ -15,18 +15,19 @@ class class_auth_backend_basic
 {
 	
 	/**
+	 * @var array {list<\davina\sources\interface_source>}
 	 */
-	private \davina\sources\interface_source $source;
+	private array $sources;
 	
 	
 	/**
 	 */
 	public function __construct(
-		\davina\sources\interface_source $source
+		array $sources
 	)
 	{
 		// parent::__construct();
-		$this->source = $source;
+		$this->sources = $sources;
 		$this->setRealm('davina');
 	}
 	
@@ -34,20 +35,38 @@ class class_auth_backend_basic
 	/**
 	 */
 	protected function validateUserPass(
-		/*string */$username,
+		/*string */$identifier,
 		/*string */$password
 	)/* : bool*/
 	{
+		$parts = \explode('-', $identifier, 2);
+		$source_name = $parts[0];
+		$username = (
+			(\count($parts) >= 2)
+			?
+			$parts[1]
+			:
+			$source_name
+		);
+		
 		$parameters = [
 			'username' => $username,
 			'password' => $password,
 		];
-		/**
-		 * @todo check for security
-		 */
-		\davina\set_parameters($parameters);
-		$data = $this->source->get(/*$parameters*/[]);
-		return ($data !== null);
+		if (! \array_key_exists($source_name, $this->sources))
+		{
+			return false;
+		}
+		else
+		{
+			$source = $this->sources[$source_name];
+			/**
+			 * @todo check for security
+			 */
+			\davina\set_parameters($parameters);
+			$data = $source->read(/*$parameters*/[]);
+			return ($data !== null);
+		}
 	}
 	
 }
diff --git a/source/overwrites/caldav_backend.php b/source/overwrites/caldav_backend.php
index 7353735..833e188 100644
--- a/source/overwrites/caldav_backend.php
+++ b/source/overwrites/caldav_backend.php
@@ -4,6 +4,7 @@ namespace davina\overwrites;
 
 require_once('vendor/autoload.php');
 require_once(DIR_LOGIC . '/helpers/call.php');
+require_once(DIR_LOGIC . '/helpers/list.php');
 require_once(DIR_LOGIC . '/helpers/ics.php');
 require_once(DIR_LOGIC . '/model.php');
 require_once(DIR_LOGIC . '/sources/_interface.php');
@@ -19,52 +20,27 @@ class class_caldav_backend
 	
 	
 	/**
+	 * @var array {map<string, \davina\sources\interface_source>}
 	 */
-	private \davina\sources\interface_source $source;
+	private array $sources;
+	
+	
+	/**
+	 */
+	private ?string $selected_source_name;
 	
 	
 	/**
 	 */
 	public function __construct(
-		\davina\sources\interface_source $source
+		array $sources
 	)
 	{
 		// parent::__construct();
-		$this->source = $source;
+		$this->sources = $sources;
+		$this->selected_source_name = null;
 	}
 	
-	
-	/**
-	 */
-	private function hash_tag(
-		string $tag
-	) : string
-	{
-		return \hash('sha256', $tag);
-	}
-	
-	
-	/**
-	 */
-	private function encode_tag(
-		string $tag
-	) : string
-	{
-		return \davina\helpers\call\convey(
-			$tag,
-			[
-				fn($x) => \strtolower($x),
-				fn($x) => \preg_replace('/ä/', 'ae', $x),
-				fn($x) => \preg_replace('/ö/', 'oe', $x),
-				fn($x) => \preg_replace('/ü/', 'ue', $x),
-				fn($x) => \preg_replace('/ß/', 'sz', $x),
-				fn($x) => \preg_replace('/\-/', '', $x),
-				fn($x) => \preg_replace('/ /', '-', $x),
-				fn($x) => \preg_replace('/[^a-zA-Z0-9_\-]/s', '_', $x),
-			]
-		);
-	}
-
 
 	/**
 	 * @todo outsource
@@ -123,6 +99,97 @@ class class_caldav_backend
 		}
 		return $vcalendar;
 	}
+	
+	
+	/**
+	 */
+	private function encode_tag(
+		string $tag
+	) : string
+	{
+		return \davina\helpers\call\convey(
+			$tag,
+			[
+				fn($x) => \strtolower($x),
+				fn($x) => \preg_replace('/ä/', 'ae', $x),
+				fn($x) => \preg_replace('/ö/', 'oe', $x),
+				fn($x) => \preg_replace('/ü/', 'ue', $x),
+				fn($x) => \preg_replace('/ß/', 'sz', $x),
+				fn($x) => \preg_replace('/\-/', '', $x),
+				fn($x) => \preg_replace('/ /', '-', $x),
+				fn($x) => \preg_replace('/[^a-zA-Z0-9_\-]/s', '_', $x),
+			]
+		);
+	}
+
+	
+	/**
+	 * @param array $parameters {
+	 *     record<
+	 *         source_name:string,
+	 *         calendar_name:string,
+	 *     >
+	 * }
+	 */
+	private function encode_calendar_identifier(
+		array $parameters
+	) : string
+	{
+		return \sprintf(
+			'%s-%s',
+			$parameters['source_name'],
+			$parameters['calendar_name']
+		);
+	}
+	
+	
+	/**
+	 * @return array {
+	 *     record<
+	 *         source_name:string,
+	 *         calendar_name:string,
+	 *     >
+	 * }
+	 */
+	private function decode_calendar_identifier(
+		string $str
+	) : array
+	{
+		$parts = \explode('-', $str, 2);
+		return [
+			'source_name' => $parts[0],
+			'calendar_name' => $parts[1],
+		];
+	}
+
+	
+	/**
+	 */
+	private function get_source(
+		$source_name
+	) : \davina\sources\interface_source
+	{
+		if (
+			($this->selected_source_name === null)
+			||
+			($this->selected_source_name === $source_name)
+		)
+		{
+			$this->selected_source_name = $source_name;
+			if (! \array_key_exists($source_name, $this->sources))
+			{
+				throw (new \Exception(\sprintf('no such source: %s', $source_name)));
+			}
+			else
+			{
+				return $this->sources[$source_name];
+			}
+		}
+		else
+		{
+			throw (new \Exception('may not change source'));
+		}
+	}
 		
 	
 	/**
@@ -132,7 +199,10 @@ class class_caldav_backend
 		$principalUri
 	)
 	{
-		$calendar = $this->source->get([]);
+		// $source = $this->source;
+		$source_name = \explode('/', $principalUri)[1];
+		$source = $this->get_source($source_name);
+		$calendar = $source->read([]);
 		$tags = [];
 		foreach ($calendar->events as $event)
 		{
@@ -143,7 +213,12 @@ class class_caldav_backend
 		}
 		$result = \array_map(
 			fn($tag) => [
-				'id' => $this->hash_tag($tag),
+				'id' => $this->encode_calendar_identifier(
+					[
+						'source_name' => $source_name,
+						'calendar_name' => $this->encode_tag($tag),
+					]
+				),
 				'uri' => $this->encode_tag($tag),
 				'principaluri' => $principalUri,
 				'{DAV:}displayname' => $tag,
@@ -187,8 +262,12 @@ class class_caldav_backend
 		$calendarId
 	)
 	{
-		$tag = $calendarId;
-		$calendar = $this->source->get([]);
+		$calendar_identifier = $this->decode_calendar_identifier($calendarId);
+		$source_name = $calendar_identifier['source_name'];
+		$source = $this->get_source($source_name);
+		$tag = $calendar_identifier['calendar_name'];		
+		$calendar = $source->read([]);
+		
 		$result = \array_map(
 			fn($event) => [
 				'calendarid' => $calendarId,
@@ -207,7 +286,7 @@ class class_caldav_backend
 					fn($event) => \in_array(
 						$tag,
 						\array_map(
-							fn($x) => $this->hash_tag($x),
+							fn($x) => $this->encode_tag($x),
 							$event->tags
 						)
 					)
@@ -227,7 +306,12 @@ class class_caldav_backend
 	)
 	{
 		$id = $objectUri;
-		$calendar = $this->source->get([]);
+		$calendar_identifier = $this->decode_calendar_identifier($calendarId);
+		$source_name = $calendar_identifier['source_name'];
+		$source = $this->get_source($source_name);
+		$tag = $calendar_identifier['calendar_name'];		
+		$calendar = $source->read([]);
+		
 		$events = \array_values(
 			\array_filter(
 				$calendar->events,
diff --git a/source/overwrites/principal_backend.php b/source/overwrites/principal_backend.php
index be59c3f..d4194e2 100644
--- a/source/overwrites/principal_backend.php
+++ b/source/overwrites/principal_backend.php
@@ -3,6 +3,7 @@
 namespace davina\overwrites;
 
 require_once('vendor/autoload.php');
+require_once(DIR_LOGIC . '/helpers/list.php');
 
 
 /**
@@ -12,17 +13,39 @@ class class_principle_backend
 {
 	
 	/**
+	 * @var array {map<string, \davina\sources\interface_source>}
 	 */
-	public function getPrincipalsByPrefix($prefixPath)
+	private array $sources;
+	
+	
+	/**
+	 */
+	public function __construct(
+		array $sources
+	)
 	{
-		throw (new \Exception('not implemented: getPrincipalsByPrefix'));
-		/*
-		return [
-			[
-				'uri' => 'principals/dummy',
+		$this->sources = $sources;
+	}
+	
+	
+	/**
+	 */
+	public function getPrincipalsByPrefix(
+		$prefixPath
+	)
+	{
+		return \davina\helpers\list_\map(
+			\array_keys($this->sources),
+			fn($source_name) => [
+				'uri' => \davina\helpers\string_\coin(
+					'principals/{{name}}',
+					[
+						'name' => $source_name,
+					]
+				),
+				'{DAV:}displayname' => $source_name,
 			]
-		];
-		 */
+		);
 	}
 
 	
@@ -32,7 +55,6 @@ class class_principle_backend
 		$path
 	)
 	{
-		// throw (new \Exception('not implemented: getPrincipalByPath'));
 		$parts = \explode('/', $path);
 		$username = $parts[1];
 		return [
diff --git a/source/sources/_factory.php b/source/sources/_factory.php
index 0721a84..fe04e0f 100644
--- a/source/sources/_factory.php
+++ b/source/sources/_factory.php
@@ -6,26 +6,21 @@ require_once(DIR_LOGIC . '/sources/ics_feed.php');
 
 
 /**
- * @param array $descriptor {
- *     record<
- *         kind:string,
- *         data:any
- *     >
- * }
  */
 function make(
-	array $descriptor
+	string $kind,
+	$data
 ) : interface_source
 {
-	switch ($descriptor['kind'])
+	switch ($kind)
 	{
 		case 'ics_feed':
 		{
 			return (
 				new class_source_ics_feed(
-					$descriptor['data']['url'],
-					($descriptor['data']['lifetime'] ?? (60 * 15)),
-					($descriptor['data']['combine'] ?? false)
+					$data['url'],
+					($data['lifetime'] ?? (60 * 15)),
+					($data['combine'] ?? false)
 				)
 			);
 		}
@@ -35,7 +30,7 @@ function make(
 				new \Exception(
 					\sprintf(
 						'unhandled source kind: %s',
-						$descriptor['kind']
+						$kind
 					)
 				)
 			);
@@ -44,4 +39,4 @@ function make(
 	}
 }
 
-
+ ?>
diff --git a/source/sources/_interface.php b/source/sources/_interface.php
index bfb8ab2..bcb414d 100644
--- a/source/sources/_interface.php
+++ b/source/sources/_interface.php
@@ -16,7 +16,7 @@ interface interface_source
 	 *     >
 	 * }
 	 */
-	public function get(
+	public function read(
 		array $parameters
 	) : \davina\model\struct_calendar
 	;
diff --git a/source/sources/ics_feed.php b/source/sources/ics_feed.php
index 2db9513..35df9e6 100644
--- a/source/sources/ics_feed.php
+++ b/source/sources/ics_feed.php
@@ -121,7 +121,7 @@ class class_source_ics_feed
 						(
 							$this->combine
 							?
-							['combined']
+							['all']
 							:
 							$vevent->categories
 						)
@@ -178,7 +178,7 @@ class class_source_ics_feed
 	/**
 	 * [implementation]
 	 */
-	public function get(
+	public function read(
 		array $parameters
 	) : \davina\model\struct_calendar
 	{