Q. How do I Harvard reference the EECERA ethical guidelines for early childhood?

Bertram, T. et al. (2025) 'EECERA ethical code for early childhood researchers', European Early Childhood Education Research Journal, 33(1), pp. 4-18. Available at: https://doi.org/10.1080/1350293X.2024.2445361

Example in your writing: 

The revised EECERA ethical code (Bertram et al, 2025) recognises the global issue of sustainability and technological advancements.