3.1.1.1. Video: SP Cluster Pronunciation | English Pronunciation - YouTube - https://www.youtube.com/watch?v=3k7jN4kX4U

3.1.1.2. Video: How to Pronounce SP Clusters - YouTube - https://www.youtube.com/watch?v=0z1gT2g3w5s

3.1.1.3. Article: English Consonant Clusters: SP - Pronunciation Studio - https://pronunciationstudio.com/sp-clusters/

3.1.1.4. Article: Consonant Clusters in English - Hadar Shemesh - https://hadarshemesh.com/magazine/consonant-clusters/