  In the papers Carmona and Durrleman [7] and Bjerksund and Stensland [1],
closed form approximations for spread call option prices were studied under the
log normal models. In this paper, we give an alternative closed form formula
for the price of spread call options under the log-normal models also. Our
formula can be seen as a generalization of the closed-form formula presented in
Bjerksund and Stensland [1] as their formula can be obtained by selecting
special parameter values to our formula. Numerical tests show that our formula
performs better for certain range of model parameters than the closed-form
formula presented in Bjerksund and Stensland [1].
