18. Each part of any pension corresponding to each of the indexing methods applicable thereto and each pension credit must be reduced by the amount of any pension corresponding to each of the indexing methods applicable thereto as well as by the amount of each pension credit that would be obtained on the basis of the sums awarded to the spouse at the date of assessment. The same applies where the amount paid to the spouse comes partly from the value of any pension corresponding to years or parts of a year of service relative to the Teachers Pension Plan, the Civil Service Superannuation Plan and the Government and Public Employees Retirement Plan that were transferred to the Pension Plan of Certain Teachers, for each of those cases.