diff --git a/DESCRIPTION b/DESCRIPTION
index 3bf20c5be4ddf547e8602e176fc3b7d246296013..5aaf6fbebd71c2f139455571b2f980f576ea12ba 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,5 +1,5 @@
 Package: gmGeostats
-Version: 0.10-8
+Version: 0.10-8-9000
 Date: 2021-07-15
 Title: Geostatistics for Compositional Analysis
 Authors@R: c(person(given = "Raimon", 
diff --git a/NEWS.md b/NEWS.md
index acbde3e5b03786d4cddef07c30f4bbbc4dfdfb8e..0ca5835417bea9846232ba015ff0c3c305cc7f14 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,3 +1,11 @@
+# gmGeostats 0.10.8-9000
+
+* (2021-07-15) documented abstract union classes, specifying required methods for the member classes
+
+# gmGeostats 0.10.8
+
+(release of polished 0.10.7.900x dev versions)
+
 # gmGeostats 0.10.7.9006
 
 * new vignette "How to register new layer datatypes", with a howto adapt gmGeostats to deal with your very special data type (with an example for regionalized circular data)
diff --git a/vignettes/register_new_layer_datatype.Rmd b/vignettes/register_new_layer_datatype.Rmd
index ce6fc0741f27529f28437c97eb5b0ed9d33b079b..6e9046f5dc4edb7f950c3b0137469156fca5d958 100644
--- a/vignettes/register_new_layer_datatype.Rmd
+++ b/vignettes/register_new_layer_datatype.Rmd
@@ -150,7 +150,7 @@ image_cokriged.circular = function(x, ...){
 image_cokriged(theta.prds.back, ivar="theta")
 ```
 
-## An excursion on superclasses classes 
+## An excursion on superclasses 
 
 "gmGeostats" uses a mixture of S3 and S4 classes to manage the several kinds of objects, S3 classes mostly preferred for simple configuration objects, models and data elements, and S4 classes mostly in use for large compound spatial models and data containers. S4 classes, though being somewhat more complex to handle and slightly slower, have the advantage to allow for multiple dispatch, which this package extensively uses. S4 classes require its fields (called "slots") to strictly belong to a specific class. To handle this condition, and at the same time allow for multiple methods of specification, estimation, fitting and prediction of spatial models and random functions, "gmGeostats" provides a series of abstract classes controlling allowing certain fields to contain certain kinds of objects: