Ova is the plural for ovum, which is the female gamete (sex cell). An ovum can also be called an egg. Its function is to fuse with a sperm cell during fertilization, and create a zygote. This can then go on to create a new organism (offspring).
Three years ago, more than 1.4 million individuals apparently decided they had better things to do than file their 2006 tax returns, even though they were due refunds. In total, more than $1.3 billion worth of refunds from that tax year is still sitting in the Internal Revenue Service account. Taxpayers can still get their old refund checks, which the IRS says could amount to more than $800 for some folks. But the claim, via a 2006 Form 1040, must be made by April 15.
Without returns being filed the statue of frauds never starts running. Therefore all 15 years are technically open. I'd strongly suggest that you proceed with the earliest practical open year first which would be 2011 and work your way forward. Then start with the earliest year and work your way forward to 2010.