Where and how I could find a ref book of deceased people,to find the date of
my father departed
Unfortunately there is neither a referencebook nor a database available, which would contain information on the deceased all over the country. What I recommend you to do is to find out the city or county where your father lived and contact the parish register office. However, if he was killed in the Second Worldwar (1939-1945) you most propably will find this information in the address http://tietokannat.mil.fi which contains the file of fallen soldiers in the war 1939-45. This database is available also in English. If you are interested in genealogic research I recommend you to check http://www.genealogia.fi , which has excellent links, too. Another useful address http://www.familysearch.org , which is run by the Church of Jesus Christ of Latter Day Saints.