diff --git a/knowledge base/cloud computing/aws/s3.md b/knowledge base/cloud computing/aws/s3.md
index ac4bd61..b55dcff 100644
--- a/knowledge base/cloud computing/aws/s3.md	
+++ b/knowledge base/cloud computing/aws/s3.md	
@@ -152,6 +152,9 @@ Examples: [1][lifecycle  configuration examples], [2][s3 lifecycle rules example
 - [Configure notification for lifecycle rules][lifecycle  configure notification]
 - AWS' [CLI]
 - [Expiring Amazon S3 objects based on last accessed date to decrease costs]
+- [Understanding and managing Amazon S3 storage classes]
+- [Using S3 Intelligent-Tiering]
+- [Amazon S3 cost optimization for predictable and dynamic access patterns]
 
 ### Sources
 
@@ -176,6 +179,7 @@ Examples: [1][lifecycle  configuration examples], [2][s3 lifecycle rules example
 [s3 lifecycle rules examples]: ../../../examples/aws/s3.lifecycle-rules
 
 <!-- Upstream -->
+[Amazon S3 cost optimization for predictable and dynamic access patterns]: https://aws.amazon.com/blogs/storage/amazon-s3-cost-optimization-for-predictable-and-dynamic-access-patterns/
 [amazon s3 storage classes]: https://aws.amazon.com/s3/storage-classes/
 [cli subcommand reference]: https://docs.aws.amazon.com/cli/latest/reference/s3/
 [expiring amazon s3 objects based on last accessed date to decrease costs]: https://aws.amazon.com/blogs/architecture/expiring-amazon-s3-objects-based-on-last-accessed-date-to-decrease-costs/
@@ -184,5 +188,7 @@ Examples: [1][lifecycle  configuration examples], [2][s3 lifecycle rules example
 [lifecycle  configuration examples]: https://docs.aws.amazon.com/AmazonS3/latest/userguide/lifecycle-configuration-examples.html
 [lifecycle  configure notification]: https://docs.aws.amazon.com/AmazonS3/latest/userguide/lifecycle-configure-notification.html
 [lifecycle  general considerations for transitions]: https://docs.aws.amazon.com/AmazonS3/latest/userguide/lifecycle-transition-general-considerations.html
+[Understanding and managing Amazon S3 storage classes]: https://docs.aws.amazon.com/AmazonS3/latest/userguide/storage-class-intro.html
+[Using S3 Intelligent-Tiering]: https://docs.aws.amazon.com/AmazonS3/latest/userguide/using-intelligent-tiering.html
 
 <!-- Others -->