diff --git a/README.txt b/README.txt
index 4603eec..0165335 100644
--- a/README.txt
+++ b/README.txt
@@ -12,8 +12,8 @@ SWAP: 2x RAM
 Disk: 20GB OR your requirement as per user count.
 CPU: 2 or 4 core.
 
-# Operating System and Package Version:
-OS: Centos 7
+# Operating System and Components Version:
+OS: Centos 7.x (Minimal Package)
 Dovecot: 2.2.36
 Postfix: 2.10.1
 SpamAssassin: 3.4.0
@@ -22,6 +22,10 @@ Postfixadmin: 3.3.8
 Roundcubemail: 1.4.11
 Apache: 2.4.6
 
+Reference Link:
+https://github.com/postfixadmin/postfixadmin
+https://github.com/roundcube/roundcubemail
+
 # Install required packages.
 
 yum install -y epel-release yum-utils http://rpms.remirepo.net/enterprise/remi-release-7.rpm vim net-tools ; yum-config-manager --enable remi-php74 ; yum -y install postfix dovecot dovecot-mysql dovecot-pigeonhole mariadb-server telnet mailx wget ; yum -y install spamassassin ; yum install -y libopendkim opendkim; yum install -y postgrey spamassassin spamass-milter-postfix spamass-milter; yum install -y clamav-filesystem clamav-server clamav-update clamav-milter-systemd clamav-data clamav-server-systemd clamav-scanner-systemd clamav clamav-milter clamav-lib  clamav-devel; yum install -y php php-cli php-gd php-xml php-curl php-mysql php-zip php-mbstring php-mcrypt php-fpm php-imap php-common php-pdo php-intl php-imagick; yum update -y; yum clean all;