Exponential Integrals [S13] (Algorithm A471) CACM December, 1973 Gautschi, W. exponential integral, recurrence relations, recursive computation, continued fractions 5.12 CA731204 JB January 19, 1978 2:48 PM 2404 4 2404 2119 5 2404 2404 5 2404 2404 5 2404 2404 5 2404