;bs/bse/cf/is: describe in terms of balance command

hledger/Hledger/Cli/Commands/Balancesheet.md

@@ -12,6 +12,10 @@ with the `Asset` or `Cash` or `Liability` type, or otherwise all
 accounts under a top-level `asset` or `liability` account (case
 insensitive, plurals allowed).
 
+(This report is essentially similar to 
+"hledger balance --historical assets liabilities", 
+with liabilities sign-flipped.)
+
 Example:
 
 ```shell

hledger/Hledger/Cli/Commands/Balancesheetequity.md

@@ -11,6 +11,10 @@ declared with the `Asset`, `Cash`, `Liability` or `Equity` type, or
 otherwise all accounts under a top-level `asset`, `liability` or
 `equity` account (case insensitive, plurals allowed).
 
+(This report is essentially similar to 
+"hledger balance --historical assets liabilities equity", 
+with liabilities and equity sign-flipped.)
+
 Example:
 ```shell
 $ hledger balancesheetequity

hledger/Hledger/Cli/Commands/Cashflow.md

@@ -11,6 +11,9 @@ type, or otherwise all accounts under a top-level `asset` account
 (case insensitive, plural allowed) which do not have `fixed`,
 `investment`, `receivable` or `A/R` in their name.
 
+(This report is essentially similar to 
+"hledger balance --change assets not:fixed not:investment not:receivable".)
+
 Example:
 ```shell
 $ hledger cashflow

hledger/Hledger/Cli/Commands/Incomestatement.md

@@ -13,6 +13,10 @@ with the `Revenue` or `Expense` type, or otherwise all accounts under
 a top-level `revenue` or `income` or `expense` account (case
 insensitive, plurals allowed).
 
+(This report is essentially similar to 
+"hledger balance --change revenues expenses", 
+with revenues sign-flipped.)
+
 Example:
 ```shell
 $ hledger incomestatement