In the “Concept/Definition Maps to Comprehend Curriculum Content” Toolbox that appeared in the November 2011 issue of The Reading Teacher, 65(3), pp. 211–213, acknowledgment was erroneously omitted of the original work on concept of definition: “Concept of Definition: A Key to Improving Students’ Vocabulary” by R.M. Schwartz and T.E. Raphael, 1985, The Reading Teacher, 39(2), pp. 198–205. Additional sources for the strategy discussed in this Toolbox were Classroom Strategies for Interactive Learning by D. Buehl, 1995, Madison: Wisconsin State Reading Association, and Classroom Strategies for Interactive Learning (3rd ed.) by D. Buehl, 2009, Newark, DE: International Reading Association.