Sentence connectors and discourse markers add variety and sophistication to your writing. They show the connection between what are you saying and what has already been said or what is going to be said. There are a very large number of sentence connectors / discourse markers and it is impossible to give a complete list of them. Note that a sentence connector usually comes at the beginning of a clause.
With reference to
This is a very formal expression used mainly at the beginning of business letters. It is used to refer back to what was said before. It makes a link with a previous discourse.
With reference to your letter of 12 January, I am pleased to inform you that…
With reference to your advertisement in the New York Times of 10 January, I would like to know…
With reference to your order no 6376 placed on January 15, we are pleased to inform that your item has been shipped.
On the other hand, while, whereas
These expressions are used to balance two ideas that contrast, but do not contradict each other.
On the other hand
James is very reserved. His brother, on the other hand, is sociable.
Tablet computers are more portable than laptops. The latter, on the other hand, offer the full functionality of a computer.
Arranged marriages are quite common in the Middle East. In the West, on the other hand, they are unusual.
The job wasn’t very interesting. On the other hand, it was well paid.
While and whereas
I like to live in the city, while / whereas my wife prefers the country.
While I admire your courage, I think you should not go on this dangerous journey.
While / whereas some languages have more than 30 different vowel sounds, English has just five.
Susie is hardworking whereas / while her brother is very lazy.
However and nevertheless
However and nevertheless emphasise the fact that the second point contrasts with the first.
However hard she ran, she could not catch up.
She ran hard; nevertheless, she could not catch up.
There was little hope of success; nevertheless, they decided to perform the operation.