diff --git a/doc/source/reference_manual/ctbutterfly.rst b/doc/source/reference_manual/ctbutterfly.rst
index 0a6b7ca..95355f7 100644
--- a/doc/source/reference_manual/ctbutterfly.rst
+++ b/doc/source/reference_manual/ctbutterfly.rst
@@ -3,18 +3,19 @@
 ctbutterfly
 ===========
 
-Computes butterfly.
+Computes butterfly diagram for a power law model.
 
 
 Synopsis
 --------
 
 Calculates the confidence band of a power law model, taking into account the
-covariance matrix of a likelihood fit. The tool derives the envelope of 
-power law models with parameters that lie within the error ellipse. It 
-outputs an ASCII file in column separated value (CSV) format containing 
-the results. Each row in the result file corresponds to an energy. The 
-columns give the energy in MeV, the fitted intensity in ph/cm2/s/MeV,
+covariance matrix resulting from a maximum likelihood fit. The tool derives
+the envelope of all power law models whose prefactor and spectral index fall
+within the error ellipse that is associated with the covariance of the 
+parameters. It outputs an ASCII file in column separated value (CSV) format
+containing the results. Each row in the result file corresponds to an energy.
+The columns give the energy in MeV, the fitted intensity in ph/cm2/s/MeV,
 and the minimum and maximum intensity that envelope the power law model 
 with a given confidence (by default a confidence level of 68% is used, but 
 the level can be adjusted using the ``confidence`` parameter).
diff --git a/doc/source/reference_manual/ctlike.rst b/doc/source/reference_manual/ctlike.rst
index ccbec47..c0aeeec 100644
--- a/doc/source/reference_manual/ctlike.rst
+++ b/doc/source/reference_manual/ctlike.rst
@@ -9,13 +9,20 @@ Performs binned and unbinned maximum likelihood analysis of CTA data.
 Synopsis
 --------
 
-Determines source model parameters, such as flux, spectral index, source 
-position, and source extent from a maximum likelihood analysis of CTA data.
-The analysis can be done in a binned or an unbinned formulation of the
-log-likelihood function. For binned analysis, a counts cube produced by
-:doc:`ctbin` is required. For unbinned analysis, an event list processed by
-:doc:`ctselect` is required. Based on the input file format, ctlike
-automatically selects between binned and unbinned maximum likelihood analysis.
+Determines the flux, spectral index, position or extent of gamma-ray
+sources using maximum likelihood model fitting of CTA data. The analysis
+can be done in a binned or an unbinned formulation of the log-likelihood
+function. For binned analysis, a counts cube produced by :doc:`ctbin` is
+required. If several observations have been stacked into a single counts
+cube, an exposure cube, a PSF cube and a background cube have to be
+provided. For a single observation it is sufficient to specify the
+instrument response function. For unbinned analysis, an event list
+processed by :doc:`ctselect` is required. Based on files specified on
+input, ctlike automatically selects between binned or unbinned analysis.
+The tool can also be applied to lists of observations, specified in form
+of an observation definition file in XML format. Events of each observation
+are kept separate, and are associated to their appropriate instrument 
+response function.
 
 
 General parameters