I had learnt of these ‘Debts’ during my Youth, and had always been Impressed by it. But I could remember only 3, and was searching the net for the totality.
My search led me thousands, of course, of which I found these 3 both concise and clear. Am giving You the reference to them through links:
And came across this blog, which again specifies just 3, but I find the Epilogue the Author has written to his little piece simply Marvellous! I quote that:
“With turmoils aplenty in today’s life, I found this section most appropriate to solve many problems in today’s day and age. Hindu society today falls short of at least three of the above four parameters, donations of wealth, knowledge, getting children and caring for nature. With substantial amounts of all the four, we might just succeed in putting our nation on the right track.”