Revert "updated README"

This reverts commit d30ed7d.

README.md

@@ -4,11 +4,11 @@
   <img src="https://github.com/scrat-online/pySTARMA/blob/master/docs/pySTARMA_Logo.png"><br>
 </div>
 
-Works on python 2.7 and 3.x
+requires python 2.7
 
 pySTARMA is a Python library for modelling space-time-ARMA processes. 
-It follows the [STARIMA](https://www.jstor.org/stable/621846) model proposed by Pfeifer und Deutsch (1980).
-It implements the estimation of the space-time autocorrelation function and the partial space-time autocorrelation function.
-It also implements the model estimation by kalman filtering, based on [Cipra and Motyková(1987)](https://dml.cz/bitstream/handle/10338.dmlcz/106567/CommentatMathUnivCarol_028-1987-3_16.pdf?sequence=1) and [Cheysson (2016)](https://cran.r-project.org/web/packages/starma/starma.pdf).
+It follows the STARIMA model proposed by Pfeifer und Deutsch (1980).
+It implements the estimation of the space-time autocorrelation function and the partial space-time autocorrelation function. It also implments the model estimation by kalman filtering, based on Cipra and Motyková (1987) and Cheysson (2016).
 
-All documentation can be found in the "docs" directory
+
+All documentation is in the "docs" directory