30-second summary: CallTrackingMetrics, an SaaS provider of call tracking and contact center solutions, published an e-book aimed at helping advertisers increase revenue from their digital ads. The e-book contains a 3-step approach to maximizing performance on digital ad platforms such as Google and Facebook with the goal of achieving better efficiency from your existing media budget. You can download the free e-book, The Digital Advertiser’s Guide to Uncovering Hidden Revenue Opportunities Without Increasing Spend, from ClickZ. CallTrackingMetrics, an SaaS provider…