added links

LITERATURE

+References for formulas and algorithms, which are employed in this software.
+============================================================================
+
+
+-------------------------------------------------------------------------------
+Neutrons
+-------------------------------------------------------------------------------
+
+* (Shirane 2002), G. Shirane et al., "Neutron Scattering with a Triple-Axis Spectrometer", 2002, ISBN: 978-0521411264.
+* (Squires 2012), G. L. Squires, "Thermal Neutron Scattering", 2012, ISBN: 9781139107808.
+* (ILL Neutron Data Booklet), ISBN: 0-9704143-7-4, 2003, https://www.ill.eu/about-the-ill/documentation/
+
+
+-------------------------------------------------------------------------------
+General Mathematics
+-------------------------------------------------------------------------------
+
+* (Stoecker 1999), H. Stoecker et al., "Taschenbuch mathematischer Formeln", 1999, ISBN: 3-8171-1573-3.
+* (Kuipers 2002), J. B. Kuipers, "Quaternions and Rotation Sequences", 2002, ISBN: 0-691-10298-8.
+* (Merziger 2006), G. Merziger and T. Wirth, "Repetitorium der hoeheren Mathematik", 2006, ISBN: 3923923333.
+* (Bronstein 2008), I. N. Bronstein et al., "Taschenbuch der Mathematik", 2008, ISBN: 978-3-8171-2017-8.
+* (Scherer 2010), P. O. J. Scherer, "Computational Physics", 2010, ISBN: 978-3-642-13989-5.
+* (Scarpino 2011), M. Scarpino, "OpenCL in Action", 2011, ISBN: 9781617290176.
+* (Arfken 2013), G. B. Arfken, "Mathematical Methods for Physicists", 2013, ISBN: 978-0-12-384654-9.
+* (Arens 2015), T. Arens et al., "Mathematik", 2015, ISBN: 978-3-642-44919-2
+
+
+-------------------------------------------------------------------------------
+General Physics
+-------------------------------------------------------------------------------
+
+* (Schroeder 2000), D. V. Schroeder, "Thermal Physics", 2000, ISBN: 0-321-27779-1.
+* (Khomskii 2014), D. I. Khomskii, "Transition Metal Compounds", 2014, ISBN: 978-1-107-02017-7

tools/tascalc/cov.py

@@ -5,6 +5,8 @@
 # @date 30-mar-2019
 # @license GPLv3, see 'LICENSE' file
 #
+# for a good explanation of the covariance matrix method, see, e.g., (Arens 2015), p. 795.
+#
 
 import os
 import tas

tools/tascalc/tas.py

@@ -32,12 +32,14 @@ def rotate(_axis, vec, phi):
 
 # get metric from crystal B matrix
 # basis vectors are in the columns of B, i.e. the second index
+# see (Arens 2015), p. 815
 def get_metric(B):
 	#return np.einsum("ij,ik -> jk", B, B)
 	return np.dot(np.transpose(B), B)
 
 
 # cross product in fractional coordinates
+# see: (Arens 2015), p. 815
 def cross(a, b, B):
 	# levi-civita in fractional coordinates
 	def levi(i,j,k, B):
@@ -50,11 +52,13 @@ def cross(a, b, B):
 
 
 # dot product in fractional coordinates
+# see: (Arens 2015), p. 808
 def dot(a, b, metric):
 	return np.dot(a, np.dot(metric, b))
 
 
 # angle between peaks in fractional coordinates
+# see (Arens 2015), p. 808
 def angle(a, b, metric):
 	len_a = np.sqrt(dot(a, a, metric))
 	len_b = np.sqrt(dot(b, b, metric))