format
The format is:
Time-Series [1:144] from 1960 to 1972: 112 118 132 129 121 135 148 148 136 119 ...source
Box, G. E. P., Jenkins, G. M. and Reinsel, G. C. (1994) Time Series Analysis, Forecasting
and Control. Second Edition. New York: Prentice-Hall.