Are All Perfect Numbers Even?/Progress/Minimum Size/Historical Note

Historical Note on Minimum Size of Odd Perfect Number
published a proof in $1968$ that an odd perfect number is greater than $10^{36}$.

published a proof in $1973$ that an odd perfect number is greater than $10^{50}$.

and published a proof in $1989$ that an odd perfect number is greater than $10^{160}$.

, and  published a proof in $1991$ that an odd perfect number is greater than $10^{300}$.

and published a proof in $2012$ that an odd perfect number is greater than $10^{1500}$.