Very well mind. com        https://www.verywellmind.com/what-is-sand-tray-therapy-4589493

GoodTherapy.org              https://www.goodtherapy.org/learn-about-therapy/types/sand-tray-sand-play-therapy

Sandtray Therapy: A Practical Manual (Third Edition) (2016) Linda Homeyer and Daniel Sweeney