Here is the link.

References to the future are necessary, but there is a limit to their allowed frequency.

Here’s the link to the site of a company specializing in this.

Believe it or not, you can tell the temperature from the chirping of crickets!
This fact is known as Dolbear’s Law.
Here is the link to the Wikipedia article on this.
keywords:
[chirp-rate]
[Fahrenheit]
[Celsius]
[rate of chirping]

(“a double exponential horn with bulb”)
Here’s the link to the Wikipedia article where this is discussed.

Here’s the link to the Wikipedia article on this topic.
keywords:
[mathematics]
[Kloosterman sums]
[Weyl sums]

Here is the link.