The condition of veteran Marxist leader and former West Bengal Chief Minister Mr. Jyoti Basu continues to be critical on Thursday. A team of doctors is continuously monitoring his health. Mr. Basu has been put under ventilation after he suffered breathing trouble on Wednesday. <br/> <br/>According to the nursing home sources, some positive changes of his health were found last evening. <br/> <br/>AIR Kolkata correspondent reports that the Prime Minister Dr. Manmohan Singh is arriving in Kolkata on Thursday to see the ailing leader. <br/> <br/>Besides, CPIM Geneal Secretary Mr. Prakash Karat and CPI General Secretary Mr. A. B. Bardhan are also coming to the city to see him. <br/> <br/>Mr. Basu was admitted to a private nursing home in Kolkata on first of this month following severe attack of pneumonia.<br/>