@article{
  author = {Dadsetan, Parirokh, Vahidi, Laleh, Shaghaghi, Farhad},
  title = {Dddition operation strategies in first grade students:an empirical study},
  journal = {Journal of Developmental Psychology Iranian Psychologists},
  year = {2010},
  volume = {7},
  number = {26},
  pages = {111-121},
  doi = {}
}