Our Company groups its operations into two lines of business - Cement Business and Ready-Mixed Concrete Business. The "Cement Business" refers to our manufacture and sale of cement and "Ready-Mixed Concrete Business" refers to our ready-mixed concrete, concrete products, precast concrete construction, and sundry building materials business. Our Ready-Mixed Concrete Business includes precast concrete construction which involve short-term and long-term contracts. Short-term contracts for specific projects are generally of three to six months in duration. Long-term contracts relate to specific projects with terms in excess of one year from the contract date. Revenues for these contracts are recognized under the percentage of completion method of accounting using cost-to-cost measures. Revenues from contracts using the cost-to-cost measures of completion are recognized based on the ratio of contract costs incurred to date to total estimated contract costs. Full provision is made for any anticipated losses. The majority of the long-term contracts will allow only scheduled billings and contain retainage provisions under which 5% to 10% of the contract invoicing may be withheld by the customer pending project completion. As of June 30, 2011, the amount of billed retainage which is included in accounts receivable was approximately $55,000, all of which is expected to be collected within one year. The amount of billed retainage which was included in accounts receivable at December 31, 2010 was approximately $120,000. The amount of unbilled revenue in accounts receivable was approximately $357,000 and $380,000 at June 30, 2011 and December 31, 2010, respectively. Unbilled revenue contained approximately $3,000 and $43,000 of not-currently-billable retainage at June 30, 2011 and December 31, 2010, respectively, which is expected to be collected within one year.