Vorkapić, S. T. and Babić Šikić, A. (2018) “What Pre-school Children Think about Happiness, Hope, Gratitude, Wisdom, Justice, and Optimism? The Positive Conceptual Thinking Development Study”, Journal of Positive Psychology and Wellbeing, 3(1), pp. 1-25. Available at: http://journalppw.com/index.php/JPPW/article/view/59 (Accessed: 18September2019).