diff --git a/Changelog.md b/Changelog.md
index 727df9d..aa0cde1 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -11,6 +11,12 @@
 
 ## Next release
 
+## v0.4.9
+
+- [F] volatile modifier to every integer attribute in Semaphore: meanSleepTimeAfterAwait_ms.
+- [F] volatile modifier to every integer attribute in Monitor: inPurgatory, pendingSignals and meanSleepTimeAfterAwait.
+- [F] Fabrica and Consumo allow 0 mean times now.
+
 ## v0.4.8
 
 - [T] Makefile added
diff --git a/README.md b/README.md
index b5da97a..53e388d 100644
--- a/README.md
+++ b/README.md
@@ -6,12 +6,7 @@ cclib is a Java library used in concurrency related course at Universidad Polit
 
 Run `make` or `./gradlew tasks` and follow instructions.
 
-## TODO
-
-- Tryer.java to take advantage from generics (result type) and lambda.
-- Check of mean times are really the mean of the indicated value: for
-  instance, nextInt(2 * n) generates an integer from 0 to 2n-1, this
-  means the mean is (2n-1)/2 that is not n.
+We are following the git workflow *git flow*: https://guides.github.com/introduction/flow/
 
 ## Classes in the cclib
 
@@ -51,3 +46,13 @@ The rest of the classes are used in the class assignments. Most names are in Spa
   in a shot).
 - Productor (producer): instances are threads that simulate
   production and storage of products
+
+## TODO
+
+- The library should be split, one for concurrency mechanisms, another
+  for classes used in "Concurrencia" assignments at UPM.
+- Tryer.java to take advantage from generics (result type) and lambda.
+- Check of mean times are really the mean of the indicated value: for
+  instance, nextInt(2 * n) generates an integer from 0 to 2n-1, this
+  means the mean is (2n-1)/2 that is not n.
+
diff --git a/build.gradle b/build.gradle
index 09f7e09..d179475 100644
--- a/build.gradle
+++ b/build.gradle
@@ -9,9 +9,11 @@
 plugins {
     // Apply the java-library plugin to add support for Java Library
     id 'java-library'
+    // // Support for building a distribution ZIP for a Java library (JAR file for the library and its dependencies)
+    // id 'java-library-distribution'
 }
 
-version = "0.4.8"
+version = "0.4.9"
 
 repositories {
     // Use jcenter for resolving your dependencies.
@@ -29,3 +31,14 @@ dependencies {
     // Use JUnit test framework
     testImplementation 'junit:junit:4.12'
 }
+
+// Add source to jar files (by default jar tasks only include compiled classes)
+jar {
+    from sourceSets.main.allSource
+}
+
+// Task to zip documentation
+task buildDoc(type: Zip, dependsOn: javadoc) {
+    from 'build/docs'
+    archiveName rootProject.name+"-"+version+"-docs.zip"
+}
diff --git a/src/main/java/es/upm/babel/cclib/Consumo.java b/src/main/java/es/upm/babel/cclib/Consumo.java
index ad0e297..e497b49 100644
--- a/src/main/java/es/upm/babel/cclib/Consumo.java
+++ b/src/main/java/es/upm/babel/cclib/Consumo.java
@@ -33,18 +33,10 @@ static public void establecerTiempoMedioCons(int tmc_ms) {
      * Simula el consumo de un producto.
      */
     static public void consumir(Producto prod) {
-        int t;
-        ConcIO.printfnl("inicio consumo: " + prod + "...");
-        t = random.nextInt(2 * tiempo_medio_cons_ms);
-        try {
-            Thread.sleep(t);
-        } catch (Exception ex) {
-            ConcIO.printfnl("excepción capturada: " + ex);
-            ex.printStackTrace();
-        } finally {
-            ConcIO.printfnl("fin consumo en " + t + "ms.");
-        }
-    }        
+      ConcIO.printfnl("inicio consumo: " + prod + "...");
+      simularConsumo(prod);
+      ConcIO.printfnl("fin consumo: " + prod);
+    }
 
     /**
      * Simula el consumo de un <em>paquete</em> de productos.
@@ -53,19 +45,27 @@ static public void consumir(Producto[] prods) {
         ConcIO.printfnl("inicio consumo de "
                         + prods.length + " productos...");
         for (int i = 0; i < prods.length; i++) {
-           int t;
-           t = random.nextInt(2 * tiempo_medio_cons_ms);
-           try {
-              Thread.sleep(t);
-           } catch (Exception ex) {
-              ConcIO.printfnl("excepción capturada: " + ex);
-              ex.printStackTrace();
-           } finally {
-              ConcIO.printfnl("consumido producto "
-                              + prods[i] + " en " + t + "ms.");
-           }
+          simularConsumo(prods[i]);
+          ConcIO.printfnl("producto consumido: " + prods[i]);
         }
         ConcIO.printfnl("fin consumo del paquete de "
                         + prods.length + " productos");
-    }        
+    }
+
+    /**
+     * Simula el consumo de un producto.
+     *
+     * @return tiempo de consumo
+     */
+    static public void simularConsumo(Producto prod) {
+      if (tiempo_medio_cons_ms > 0) {
+        int t = random.nextInt(2 * tiempo_medio_cons_ms);
+        try {
+          Thread.sleep(t);
+        } catch (Exception ex) {
+          ConcIO.printfnl("excepción capturada: " + ex);
+          ex.printStackTrace();
+        }
+      }
+    }
 }
diff --git a/src/main/java/es/upm/babel/cclib/Fabrica.java b/src/main/java/es/upm/babel/cclib/Fabrica.java
index f002c74..4aaf045 100644
--- a/src/main/java/es/upm/babel/cclib/Fabrica.java
+++ b/src/main/java/es/upm/babel/cclib/Fabrica.java
@@ -34,18 +34,9 @@ static public void establecerTiempoMedioProd(int tmp_ms) {
      */
     static public Producto producir() {
         Producto prod;
-        int t;
         ConcIO.printfnl("inicio producción...");
-        t = random.nextInt(2 * tiempo_medio_prod_ms);
-        try {
-            Thread.sleep(t);
-        } catch (Exception ex) {
-            ConcIO.printfnl("excepción capturada: " + ex);
-            ex.printStackTrace();
-        } finally {
-            prod = new Producto();
-            ConcIO.printfnl("fin producción: " + prod + " en " + t + "ms.");
-        }
+        prod = simularProduccion();
+        ConcIO.printfnl("fin producción: " + prod);
         return prod;
     }
 
@@ -57,21 +48,27 @@ static public Producto[] producir(int n) {
         ConcIO.printfnl("inicio producción de "
                         + prods.length + " productos...");
         for (int i = 0; i < prods.length; i++) {
-           int t;
-           t = random.nextInt(2 * tiempo_medio_prod_ms);
-           try {
-              Thread.sleep(t);
-           } catch (Exception ex) {
-              ConcIO.printfnl("excepción capturada: " + ex);
-              ex.printStackTrace();
-           } finally {
-              prods[i] = new Producto();
-              ConcIO.printfnl("producido producto: "
-                              + prods[i] + " en " + t + "ms.");
-           }
+          prods[i] = simularProduccion();
+          ConcIO.printfnl("producto producido: " + prods[i]);
         }
         ConcIO.printfnl("fin producción del paquete de "
                         + prods.length + " productos");
         return prods;
     }
+
+    /**
+     * Simula una producción de un producto.
+     */
+    static private Producto simularProduccion() {
+      if (tiempo_medio_prod_ms > 0) {
+        int t = random.nextInt(2 * tiempo_medio_prod_ms);
+        try {
+          Thread.sleep(t);
+        } catch (Exception ex) {
+          ConcIO.printfnl("excepción capturada: " + ex);
+          ex.printStackTrace();
+        }
+      }
+      return new Producto();
+    }
 }
diff --git a/src/main/java/es/upm/babel/cclib/Monitor.java b/src/main/java/es/upm/babel/cclib/Monitor.java
index a2bffeb..2d5de47 100644
--- a/src/main/java/es/upm/babel/cclib/Monitor.java
+++ b/src/main/java/es/upm/babel/cclib/Monitor.java
@@ -24,13 +24,13 @@ public class Monitor {
     * Number of threads that were moved to the purgatory and have not
     * reached heaven yet (they may have been signalled).
     */
-   private int inPurgatory = 0;
+   private volatile int inPurgatory = 0;
 
    /**
     * Number of signalled threads which have not completed monitor
     * re-entrance, not counting those signalled in purgatory.
     */
-   private int pendingSignals = 0;
+   private volatile int pendingSignals = 0;
 
    /**
     * In order to force more arbitrary interleavings on the use of
@@ -39,7 +39,7 @@ public class Monitor {
     * no sleep will be executed and the interleaving will be the
     * "natural" one.
     */
-   private int meanSleepTimeAfterAwait_ms = 0;
+   private volatile int meanSleepTimeAfterAwait_ms = 0;
 
    /**
     * Random number generator for sleeping time after await.
diff --git a/src/main/java/es/upm/babel/cclib/Semaphore.java b/src/main/java/es/upm/babel/cclib/Semaphore.java
index cc949f0..9a39d2c 100644
--- a/src/main/java/es/upm/babel/cclib/Semaphore.java
+++ b/src/main/java/es/upm/babel/cclib/Semaphore.java
@@ -16,7 +16,7 @@ public class Semaphore {
     * no sleep will be executed and the interleaving will be the
     * "natural" one.
     */
-   static private int meanSleepTimeAfterAwait_ms = 0;
+   static private volatile int meanSleepTimeAfterAwait_ms = 0;
 
    /**
     * Random number generator for sleeping time after await.
@@ -29,7 +29,7 @@ public class Semaphore {
    public Semaphore() {
       n = new java.util.concurrent.Semaphore(0,true);
    }
-   
+
    /**
     * Semaphore constructor. Internal counter initizalised to n if n
     * is positive, 0 otherwise.
@@ -38,7 +38,7 @@ public Semaphore(int n) {
       int i = n > 0 ? n : 0;
       this.n = new java.util.concurrent.Semaphore(i,true);
    }
-   
+
    /**
     * If the parameter is greater than 0 more arbitrary interleavings
     * will be introduced.