Here are several published papers that cover relevant issues to the teaching and learning of mathematics in early childhood.
Math Matters: Children's Mathematical Journeys Start Early (full report)
by Alan H. Schoenfeld & Deborah Stipek
Eager to Learn: Educating our Preschoolers (assessment excerpt)
Barbara T. Bowman, M. Suzanne Donovan, and M.Susan Burns, Editors
Committee on Early Childhood Pedagogy
National Research Council
Early Childhood Assessment: Why, What, and How
Catherine E. Snow and Susan B. Van Hemel, Editors
Committee on Developmental Outcomes and Assessments for Young Children
National Research Council
Mathematics Learning in Early Childhood: Paths Toward Excellence and Equity, Chapter 2, "Foundational Mathematics Content"
Christopher T. Cross, Taniesha A. Woods, and Heidi Schweingruber, Editors
Committee on Early Childhood Mathematics
National Research Council