Linkers

The first and second parts of the documents on linkers are hereby available.  You can also find the key for the exercises here.  As you do the exercises, please remember the following three types of linkers we have identified:

• Linkers that connect two parts of the same sentence as in the following example: We only have one week off for Easter, so we will be staying in Brussels.
• Linkers that connect two separate sentences as in the following four examples, which are different ways of saying the same thing:

1. We only have one week off for Easter.  Therefore, we will be staying in Brussels.
2. We only have one week off for Easter; therefore, we will be staying in Brussels.
3. We only have one week off for Easter.  We will, therefore, be staying in Brussels.
4. We only have one week off for Easter; we will, therefore, be staying in Brussels.

• Linkers that are covered under both the first and second types as in the four following examples:

1. Besides giving his friend a lift after work, he helped her with her grocery shopping.
2. He helped his friend with her grocery shopping, besides giving her a lift after work.
3. I am afraid I am not allowed to help you with that question.  Besides, I do not know the answer myself.
4. I am afraid I am not allowed to help you with that question; besides, I do not know the answer myself.

Note that the meaning of the word 'besides'  in the first two examples is different from its meaning in the last two examples.

In all these examples, please pay special attention to the punctuation.

Conditionals

Here you can find some information and exercises on conditionals.
Here you can find information and exercises on the same topic along with the key for the exercises. (Source: English Grammar in Use. Intermediate by Raymond Murphy)
Here you can find more mixed exercises on conditionals as well as other linking words that can be used in conditionals. There are also some exercises on expressing wishes.

Comparative and superlative

Here you can find some information with exercises on comparative and superlative. Here is the key to the exercises.

Four sources for audio and video streams

Here you can have access to the NPR of the NYC region.  It could be useful if you want to improve your listening comprehension of American English.  You can listen to the live FM broadcast or go to their show archives.  I personally like Radiolab, Selected Shorts and Fresh Air among the shows they air.
 
Here you can have access to the BBC website, which also airs on the WNYC in the mornings Brussels time.  It could be useful to improve your listening comprehension of British English.  They also have links under "Learning English", where you can find numerous tools for learners of English as a second language.
 
Here you can have access to the audio and video streams on The Economist website.  This again is a good source for improving British English listening comprehension.
 
Here you can have access to TED which is a good source for numerous talks on a very wide range of topics.  Most talks are given by Americans and Canadians, but there are also other speakers of different nationalities, including some British.

Conversation Exchange

Here you can have access to the Conversation Exchange website.

Babbel

Here is the link for Babbel Diane recommended to us.  It is an online language learning plaform.

Obligations

Positive obligations for the present, future or in general:

Stronger:
You have to put on your seat belt. (US)
We are going to/will have to go through the customs when we arrive in New york. (future)
She must put on her seat belt. (UK)
Members shall follow the club rules. (formal/legal/religious/moral codes in writing)

Weaker:
You should take off your shoes in their house.
You ought to take off your shoes in their house. (UK)

Negative obligations for the present, future or in general:

Stronger:
You cannot drive without your seat belt on. (US)
You must not drive without your set-belt on. (UK)
Thou shall not kill. (formal/legal/religious/moral codes in writing)

Weaker:
You should not enter their house with your shoes on.
You ought not to enter their house with your shoes on. (UK)

Positive obligations for the past:

Stronger:
We had to go through the customs when we came from the US to Belgium last week.

Weaker:
You should have taken off your shoes when you entered their house yesterday evening.
You ought to have taken off your shoes when you entered their house yesterday evening. (UK)

Negative obligations for the past:

Stronger: 
The waiter could not serve beer to my 17-year old cousin when we were in the US last year.  (US)

Weaker:
You should not have entered their house with your shoes on yesterday evening.
You ought not to have entered their house with your shoes on yesterday evening. (UK)

Lack of obligations for the present, future or in general:

You do not have to take off your shoes when you go through the security check at the airports in Europe.
You are not going to/will not have to take off your shoes at the security check in Zaventem airport when you arrive there. (future)

Lack of obligations for the present, future or in general:

We did not have to take off your shoes when we went through the security check at the airport last week.

I am hereby making some exercises on have to vs. must and should along with the key available.