RT Journal Article SR Electronic T1 Puzzling pyramids JF Archives of disease in childhood - Education & practice edition JO Arch Dis Child Educ Pract Ed FD BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health SP 211 OP 212 DO 10.1136/archdischild-2017-313952 VO 103 IS 4 A1 Katrina Harborne A1 Helen Williams YR 2018 UL http://ep.bmj.com/content/103/4/211.abstract AB