Is there any way to add G+ button to social sharing of articles?
It would be much appreciated.

If yes, please send a path to a file that I need to edit, and code that I need to add.

// include JavaScript
$this->addJS($this->URLtemplate() . '/js/gk.scripts.js');
$this->addJS('http://apis.google.com/js/plusone.js');
// include JavaScript
$this->addJS($this->URLtemplate() . '/js/gk.scripts.js');
$this->addJS('http://apis.google.com/js/plusone.js');
<li>
<a class="technorati" title="<?php echo JText::_('K2_ADD_TO_TECHNORATI'); ?>" href="http://www.technorati.com/faves?add=<?php echo $this->item->socialLink; ?>" target="_blank"><span><?php echo JText::_('K2_ADD_TO_TECHNORATI'); ?></span></a>
</li>
<li>
<g:plusone size="small" ></g:plusone>
</li>
<li>
<a class="technorati" title="<?php echo JText::_('K2_ADD_TO_TECHNORATI'); ?>" href="http://www.technorati.com/faves?add=<?php echo $this->item->socialLink; ?>" target="_blank"><span><?php echo JText::_('K2_ADD_TO_TECHNORATI'); ?></span></a>
</li>
<li>
<g:plusone size="small" ></g:plusone>
</li>
<li>
<g:plusone size="small" ></g:plusone>
</li>
<li>
<script src="http://platform.linkedin.com/in.js" type="text/javascript"></script><script type="IN/Share" data-counter="right"></script>
</li>
<li>
<script src="http://platform.linkedin.com/in.js" type="text/javascript"></script><script type="IN/Share"></script>
</li>