Update SEP according to the community feedback.

ecosystem/sep-0042.md

@@ -86,6 +86,8 @@ Assets metadata is published in a JSON format with the following structure:
 In order to be considered valid, an asset list must validate
 against [this JSON schema](../contents/sep-0042/assetlist.schema.json).
 
+A list should not contain the `native` (Stellar XLM) asset to prevent possible naming conflicts.
+
 ### List Publication
 
 A list providers can advertise the existence of curated asset lists through their
@@ -106,12 +108,13 @@ Here:
 - `provider` - Organization or entity that put together the list (max 50 chars)
 - `description` - Text description of the list to display alongside with the name (optional, max 150 chars)
 - `version` - Current list revision
+- `network` - Stellar network identifier ("public" or "testnet")
 - `feedback` - URL or Github repository address where users can report bad actors or request addition of new assets
 - `assets` - Contains an array of asset metadata entries
     - `name` - Descriptive asset name
-    - `contract` - Asset contract address in StrKey encoding (for Soroban assets)
-    - `code` - Asset code (for Classic assets)
-    - `issuer` - Asset issuer address (for Classic assets)
+    - `contract` - Asset contract address in StrKey encoding
+    - `code` - Asset code (for Classic assets) or value returned by `symbol()` function (for Soroban assets)
+    - `issuer` - Asset issuer address (for Classic assets, ignored for pure Soroban tokens)
     - `org` - Issuer organization/company (max 30 chars)
     - `domain` - FQDN of the site that hosts asset-related `stellar.toml` format
     - `icon` - Icon URL (only HTTPS protocol is supported) or IPFS hash
@@ -199,4 +202,17 @@ Therefore, application developer should either depend only on several trustworth
 the community-maintained repository of curated asset lists.
 
 Displaying the `assets.comment` contents in the interface might confuse end-users and, depending on the context,
-can be regarded as endorsements. So it's up to the application developers whether to show these comments to end users.
+can be regarded as endorsements. So it's up to the application developers whether to show these comments to end users.
+
+## Implementation
+
+- Community-managed Github repository for the [Asset Lists Catalogue]( https://github.com/stellar-asset-lists/index).  
+  It contains references to asset lists created by ecosystem providers. Client applications can use it to discover,
+  fetch available lists, and allow their users to select trusted providers in the interface. Web UI for this catalogue
+  is available [here](https://stellar.expert/asset-lists).
+- Basic [JS library](https://www.npmjs.com/package/@stellar-asset-lists/sdk) that simplifies integration of asset lists
+  into web applications.
+- [StellarExpert Top50](https://api.stellar.expert/explorer/public/asset-list/top50) asset list for Stellar Pubnet.
+- [StellarExpert Testnet Top50](https://api.stellar.expert/explorer/testnet/asset-list/top50) asset list for Stellar
+  Testnet.
+