Richardson M E
Angle Orthod. 1987 Apr;57(2):155-61. doi: 10.1043/0003-3219(1987)057<0155:LTMS>2.0.CO;2.
Increase in lower third molar space in the five years following complete replacement of the deciduous dentition finds the contributions from ramus resorption and mesial movement of the first molar about equal on average, but highly variable.